Sadly, it's not surprising.
I've watched him "religiously" (Simon - don't ban me) for decades on talk shows and elsewhere.
He had a terrific sense of humour and awesome mimic skills (not Rich Little, but good).
He often spoke openly of his depression.
Most of the top comedians suffer from this dichotomy.
It is tragic.
Hopefully, whatever the next life is, he will be bringing laughter into it.