"IT" can. I'm sorry for your experience, it was traumatic. While the memories probably won't ever go away, it does sound like you need to process it more to allow it to diminish.

Everyone has those "what if" thoughts, you are not alone. We all want to have done our best, to change the world, or at least the world right around us. Fact is, people make their own decisions about their own lives. Sometimes, it isn't a good one for those around. I have some "what ifs" about my mom, yet I am reminded that there were two family professionals (myself and my sister) taking turns and working together to try and do the best ... and yet ? So if 2 of us couldn't ... then it wasn't going to be.

I'm sorry your uncle was in such a sad state that he felt the only way to get out of it was that route. If you've researched the situation and found all the details you could, then surely you realize that you could not have done anything more than you did -- or you would have! Sounds to me like he made it so you didn't know, yet I don't know how young you were or any of the situation.

The desire to have had some control is common, I think. IF we only had taken control, WE would have made things better. The idea of not having control of our environment and those we love can be unsettling at times. But even if you'd had control, it was still a decision he made, not you.
You aren't responsible for what he did. I'm sorry he messed up your life.

Now, you have a choice to realize this sad, sad thing happened but process it and then by doing so you allow the brain to file it away. You can still take those feelings and memories down out of the file from time to time, take time to think about it and maybe cry, and then put them back away and back up into the files. That's the best we can do with such memories. But they don't have to run your life any more.