I think it is an ongoing process that accelerated over the past 10 or so years. There are still many people who stigmatize mental health issues and view mental health services skeptically at best.
We've over-corrected so far now, people make up and put mental illnesses in their twitter bio to be part of some in-group. Mental illness has become a fashionable affectation. There's probably now people out there who keep theirs quiet because they don't want to get lumped with those groups.
The last thing most people want is turning their very real mental illness into an identity, but we've somehow made that the de-facto default.
It's compelling, but the international nature of the phenomenon makes me think it'd be incomplete as an explanation. Surely the stigma isn't equal everywhere
I suppose it depends on where you are. My work sent me from the US to the UK for six months in 2016. The difference in mental health stigma between these two first world nations was staggering. From what I've heard, it's even worse for eastern Europe.
