I am that friend that vanished that you are describing.
In my case, I tried talking to the friend that bothered me ( an unmedicated ADHD alcoholic mess of a friend) he told me to fuck off.
I even stopped hanging out with my old group of friends that involved this guy that I described because it became this: male anger space to vent off, suicide jokes, complain about work, glorify alcohol, try out different types of drugs. No, thank you, I don’t want to do a live action of Rick n Morty.
There is no talking with a group where everyone decided to stay together on a shitty decision. I tried once and they got really angry and made me the wrong one for going to the gym, waking up early, quitting alcohol, etc.
I still keep in touch from afar and now, almost 10 years later, some of them are saying " yeah, the doctor told me to drop the alcohol", " yeah now I found the right meds for me and I aint as angry"
Everybody goes at their own pace, but expecting other friends to stay with you during this journey is ludicrous.
I went my way and although it hurt, sometimes its the best thing you can do for your mental health and integrity
I feel you.
On your 3rd paragraph, I also have no idea why this happens, but we are not the only ones. Maybe people get the idea we became too self-centered?
I cannot comment on you because I don’t know you, but in my case, if I were to be self-critic, I always focus too much on my career, wife, hobbies, household chores, family… friends were always the last priority on my schedule. People pick up on that quickly, idk.
I do have some friends though who are low maintenance and with these I find its much easier to keep friends with. We can go 6 months without seeing each other and its still fun to get together.