Why/How do Cyanobacteria Produce Toxins?

I’ve been doing some research on the versatility of nitrogen-fixing cyanobacteria, particularly of the genus Anabaena, and I often run into safety hazards and have to add extra steps to my procedures because of the toxins produced by the genus. After doing some reading, I’ve found that most cyanobacteria produce toxins (collectively dubbed “cyanotoxins”). The wide variety of different structures and mechanisms of the toxins across multiple genera is astounding, especially because some of them are carcinogens, which would logically affect the host unless a mechanism to prevent this had evolved. This tells me that a lot of evolutionary “effort” must have been put into the evolution of toxin production in cyanobacteria. Originally, I just thought that the toxins were a natural part of their metabolism that evolved normally because these compounds didn’t affect them in the same way as they did us. Now that I see the Huge, variable trend throughout the class, I have begun to think otherwise. My questions are as follows:

1. What is the evolutionary basis for the production of cyanotoxins by cyanobacteria
2. Are the cyanotoxins a necessary part of the bacteria’s metabolism, or can they be eliminated by way of genetic engineering without directly affecting the success of the organism?
3. How do cyanobacteria cope with the constant exposure to native carcinogens?

These questions are only the major ones that I have, so any extra information is greatly appreciated