What to do to understand a presentation if you didn't understand anything?

If you did not understand a presentation, if you have an email or slack link to the original presenter, ask them some questions about the presentation that you have. Make sure they are good questions though, specific questions. First thank them for the presentation. Make yourself look like you put in at least some effort at researching prior to asking the question. But most presenters will gladly respond because it tells them that people are actually paying attention to their work.

I think it's safe to assume that the presenters in question either haven't developed the skills needed to make presentations --OR-- don't want to give the presentations and thus are "phoning it in" with minimal effort --OR-- lack mastery in the subject-matter and are simply "cargo-culting" a talk out of disparate pieces of information they don't fully understand.

Consider that if you don't understand what's going on, there are likely others in the room that aren't following. It could be a huge waste of time and effort for multiple people including the presenters.

Unfortunately, by the time someone has put together a deck and is starting on their obfuscated presentation, it's really too late to do anything about it. Only the most skilled presenters are able to adapt their talk to fit an audience on the fly-- so prompting them with pointed questions during the talk isn't going to help much unless you just want one piece of information.

What you'll want to do is to raise the standards of the talks by getting OTHER people to give the talks.

One way I've seen this done is to actually get interns or juniors to make the presentations. The subject matter experts provide content, help, and review. Another person who is skilled at presentation coaches the interns/juniors about how to put together a good talk. In the end you get a talk from someone who really worked hard on making a cogent presentation, who understands what parts are difficult because they overcame it themselves, and the subject-matter experts are freed from having to give presentations (which they probably dread).

When

it's vital for me to understand the presentation

and the presenter does a poor job of... ugh... presenting, you schedule a follow-up "meeting" and include a few other folks for whom you think it may also be vital, or, absent those, at least someone to add weight to the invitation.

Powerpoint decks are not meant to be understood, without context, by anyone except the presenter. However, using the unintelligible scribbles you made during the original presentation, the copy of the deck, and whatever you can recollect from the speech, you can try to build a mental picture of what was being explained.

Then, after many iterations of rescheduling the follow-up call, when you finally get on the phone/webex/zoom/whatever with the presenter, you set the scene by explaining how you are grateful for the opportunity, explain why it is important for you and the entire organization to get things right, describe briefly what you have understood so far, then -- let the former presenter speak, but lead with questions that are important to you. In this smaller setting the awkwardness of trying to explain "obvious" things, and of asking "stupid" questions, will be significantly reduced.

If necessary, you will repeat this excercise two or three times, until you get to where you need to be, or give up and move on.

Ask the presenter before the meeting the following question...

Who’s the target audience for this presentation?

That will give you an idea if it’s relevant to your domain or not - and give you a good sense if you should be understanding it or not (or if you should be even in the meeting at all). Some folks include more people on the invite than necessary as a “just in case”.

E.g. If the meeting is about setting up maven / eclipse and you’re a c# / .net developer, you can pretty much skip the meeting/presentation.

If it’s something that should be familiar to you but it’s not, ask the presenter after the meeting

Hey! You threw out this term and that term...what are those?

Some folks think that if they know something, it’s industry standard so the missing link could be as simple as a Wikipedia article or similar.

E.g. “Strategy, Factory, State, MVC” without having read “Design Patterns” wouldn’t make any sense.

The problem is: you let it get too far.

I mean, if I'm presenting something on using Generics in C# Abstract Classes - and towards the end of the presentation, someone asks, "What's a Generic?" ... I'm not going to know how to respond. I can't go back and give the whole presentation over again.

... but if someone, in the third sentence, raises their hand and asks, "What's a Generic?" I'll be able to say, "You're right - let me go back and explain what that is before we go any further."

Basically, the longer you go without asking for clarification on a point, the harder it is for the person to clarify; and that gets compounded for each item that needs clarification.

From your perspective, there are two skills you need to keep in mind:

The ability to speak up and request clarification quickly. This can be nerve-wracking, especially if you're socially anxious. But if you intend to understand the presentation, you kinda have to be able to do this sometimes (or hope someone else has the same incomprehension and asks themeselves.)

The ability to know when clarification will help or bog down a presentation. If I was giving a "Using Generics in C# Abstract Classes", and someone asked what a Generic was, I'd immediately circle back and say, "You're right - let me explain quick what a Generic is and why they're used; it's going to be important for what we're about to go over". If someone asked, "What's C#?" - I'm going to tell them that the presentation isn't aimed at them and is assuming at least moderate level of knowledge on the language. And there's nothing wrong with this.

To a more general level? You might consider suggesting to management that some courses in public speaking, public presentation, etc, might be in order. Presentation isn't a natural skill, and people generally suck at it by default.

I don't know if this helps, there's a tradition of using the business phrase ".. a stupid question .." in a self-deprecating way.

Hence, I am forever saying in meetings ..

"Let me ask a stupid question ... {what client is this actually?}"

"Let me be the one to ask a dumb question .. {does this have to do with computers?}"

"As usual, I will ask the dumb questions ... {is this something we have to do?}"

Generally whenever anyone plays the "dumb question..." phrase card, you are met with a chorus of good, solid, corporate, there are no dumb questions!, and it's better to ask nows!, and dumb questions save times! - !!!

It's kind of a social-business formalism.

"Everyone knows" that what's really being said is some combination of "I am really lost" or "This presentation is utterly hopeless" or "Someone has made some drastic basic mistake."

But instead you say "Oh no! Looks like I'm the one asking a dumb question again ...!"

Ands everyone cheerfully replies with motivational-poster yee-ha.

I imagine in - say - Japan they have some highly-developed formalism for this. Like, everyone coughs twice or something, and this is understood to mean "We support you, but your presentation is crap. WTF dude."

In the US/UK/West generally, there's the "here's a dumb question!" formalism.

It may help!