You can explain this story the same way as you did here, with perhaps a little less bitterness. Something like:
“This was my first job. I thought I needed the experience, even though I knew the company was somewhat toxic. It was not going well, but thought I’d stay because it would look bad if I left. Then I told my boss things weren’t going well and he fired me, which to be honest was a relief. So all in all it was a big mistake and a waste of time, but at least now I know that company culture is important and this is also why I want to join your great company blah blah blah”
You can explain this story the same way as you did here, with perhaps a little less bitterness. Something like:
“This was my first job. I thought I needed the experience, even though I knew the company was somewhat toxic. It was not going well, but thought I’d stay because it would look bad if I left. Then I told my boss things weren’t going well and he fired me, which to be honest was a relief. So all in all it was a big mistake and a waste of time, but at least now I know that company culture is important and this is also why I want to join your great company blah blah blah”