I've worked at the full spectrum from great to terrible (and eventually one that went legally fraudulent) companies.

You're right that there can be a problem at small companies when you hire someone out of a toxic company. Some people love the fresh start and are so happy to finally be in a healthy environment that they thrive.

Some people are so broken from toxic previous employers that they can't adapt. We hired a lot of people out of a competitive Big Tech office and it was probably a 50/50 flip of the coin if they were going to be great to work with or toxic political monsters. I had to have so many difficult conversations with people who could only see their coworkers and other teams as competitors who had to be defeated that I nearly had a prepared speech on the topic. The politics and attempted backstabbing was insane. It was also weird that they thought it was going to work at a small company where we knew the people they were trying to backstab for years.

Stop trying to hire folks from AWS and this won't happen. Micrsoft is famous for "rest and vest" and a far less toxic culture as a result. You could also try hiring from Intel, where the internal "great place to work" propaganda is known as "great place to leetcode" because usually the work pace is so lax that its seem as a stepping stone for further advancement on your own time...