I was under the impression you are born with multiple personality disorder and you don't develop or catch it. He had attention deficit but was able to function on a high level not unlike someone with borderline autism.That's looks like self-medicating to me. Which came first: clearly the bipolar, ATD, etc, etc.
Along with the alcohol there is mention of sleeping pills, maybe lots of coke too with reference to the substance abuse.
In my experience, bipolar's can be the life and soul of the party at least initially, but once you get to know them and the mask slips then like with other mental disorders they're not that attractive to be around and will ultimately bring the party down. Of course, there's different types of mania, but I've known a couple of bipolars over the years and they've all had a very special ability and charisma in charming people into their world until much later they are rejected when people wake-up and realise they are off the beaten track in someone else's nightmare.
I just found it interesting his family kept feeding him extreme extracurricular activities that probably made it worse. Climbing mountains or yoga were distractions to what was truly bothering him. It delayed his suicide.