Reason for a transaction and 2 cancelling transactions being stuck?

I sent a transaction. Shortly after, I decided to cancel it, so made a cancel transaction (using MetaMask). After a while, since nothing was happening, I sped up the cancel transaction, i.e. sent a 2nd cancel transaction with more gas.

Now 20 minutes have passed and I see all 3 transactions in Etherscan with state "pending". All 3 show the expected (?) status:

Duplicate Nonce (found 2 other duplicate Pending Txn #1, #2 with the same `From` Account Nonce)

I also confirmed that all have the same nonce (which I assume causes the message above).

My question is why does this happen? Is it some sort of network congestion or something specific to my account? And what can I do to fix it? Do I’ve to keep sending cancel transactions with more gas (MetaMask doesn’t seem to allow to enter a high amount from the beginning)?

Edit: I was able to solve it by retrying the original transaction. The retry transaction was marked as "failed" and the other 3 disappeared. Effectively it was cancelled. Still would like to understand this better.