OP, influence is a skill. It sounds like you may need practice in it. Take this as a challenge going forwards -- can you have the kind of impact that would come from saying what you see and being honest, WITHOUT getting fired for it?
Part of this might be on your management. Impossible to tell given the information we have. It's possible you could luck out and find someone who is more comfortable with pushback next time. But it's very possible that even with the people you were dealing with, you could have found a way to say this stuff, have a positive impact, and be recognized for it, all without being fired?
Also, I'm reading WAY between the lines here, but it sounds like stuff might have boiled up to the surface and you could have been speaking from a place of "I can't take it anymore, here's all the stuff I bottled up about why this is wrong". Maybe think about whether that's the case. If you let emotion get in the way of reasoned discussion, then it becomes about "here's why you suck" and not "let's think about this course of action in a different way". Which no one will react well to.