I have a story that backfired. I had a team of 5 developers that were working in a product. The company had been trying to build the product for several years. When I saw the architecture they were using I tried to convince the architect to make some changes. They wouldn't do it. They wouldn't even let me touch the code. I was a manager I wasn't supposed to get involved. So I thought. "It is better to ask for forgiveness than to ask for permission". So I started to build the product from scratch. I had plenty of time and no one cared what I did. After 5 or 6 months I already had a product that was way a head than the official product. When I tried to show it to my manager he got really mad. He literally screamed at me. That was 1.5 years ago. I went in a depression for a long time. They fired the architect. They fired my manager. The developers had to spin their wheels for a long time. Then they left. And the product is still not ready.
From the data you provide, this doesn't sound like it backfired at all.
In a difficult situation, you're the only one who did the right thing and it led to nothing. This says more about others than it says about you.
You boss got mad, yelled at you, and got fired. That's his problem, not yours. Others suffered or got fired and work wasn't finished. Again, their problem, not yours.
I think you should hold your head high and be proud. You pushed the envelope and challenged others, knowing full well that they might resist. The resulting negativity had nothing to do with your efforts and everything to do things being fucked up long before you got there. Don't let the illogical actions of others upset you, don't be depressed, and most of all, don't hesitate to continue to be proactive. The rewards may seem elusive, but believe me, you will find them.
"Ask forgiveness rather than permission" is not equivalent to "forge ahead without thought for the consequences". Completely rewriting a codebase by yourself to show up a team that has been working on it for a long time might mean better code, but it's also a direct demonstration of the ineffectiveness of that team. Of course some kind of major shake-up is going to happen after something like that. Firing people might be a little extreme, but you certainly have to expect that it's a possibility.
If you don't have the stomach for directly causing people to get fired, or for conflict, then don't go out of your way to demonstrate how poorly they're doing their job. Find your way out to something else, and let them do themselves in.
No one was fired as a consequence of what I did. They were fired because time passed and there were no results. If I had been able to convince my boss I think we would have been successful. At one moment I thought about going one level up in the organization, I decided to be loyal to my boss so I kept my mouth shut.
