I will note that nothing above contradicts what I said - if they kept everything on WoW, it is entirely possible they'd have made more.
Yes, almost all companies try to diversify, sure. Quite a lot (most) of such attempts to diversify are very ineffective and quite a lot end up being a waste of time.
I am saying this has happened here with Blizzard - their attempts to diversify from WoW into other games are questionable, it is completely unclear whether they were worth it. The biggest issue is that I think these attempts had an adverse effect on their flagship product = WoW, which even today is the product that largely finances all these experiments.
"SOME outliers can sell one product for decades and still profit (I can't think of any at the moment, but I'm sure there are some)" --- if you want companies that largely failed to diversify, there is no shortage of them. There's Google, for example. 90% of their business remains tied to a single product. They have been trying to diversify for something like 8 years already, keep failing.
I suggest you temper your tone, your reply was neither very logical nor knowledgeable.