Warning: This is a personal opinion, take it with a grain of salt.
The situation in Blizzard is … sad … but well deserved. Blizzard has lost any creativity and aims only to get as much money as possible, by destroying their well established brands more than 2 decades back.
Starcraft 2 - The only thing that kept it afloat was multi player (because it is so well established especially in South Korea). Campaign was boring, heavily copied Mass Effect, and story line was absolutely predictable. I played this one through myself (nostalogia from old Starcraft) - for me, there are no really memorable moments in it (that is, of course, my subjective view - others may differ - I was quite disappointed, but there were others who were happy with Starcraft 2).
World of Warcraft - I personally never played this one, large parts of community criticized how it went after The Burning Crusade, and slowly left. World of Warcraft: Classic … was quite successful attempt to get more money from original fans, for very little investment. It did work to some extent (yet the amount of players and activity went down fast in first months, it will be somewhat stable now).
Diablo Immortal - Diablo somewhat missed me - but I believe I don't need to say how much it showed how detached Blizzard from their fans is. The question “Is this some kind of April fools joke?” speaks for itself.
Warcraft 3: Rebirth - Game was developed in Malaysia if I'm not mistaken (from my point of view - it looks like Blizzard wanted to rip off older fans, as it gained a lot of revenue in case of WoW: Classic - and, well … blatantly failed it). They didn't deliver pretty much anything out of promised features, and cancelled majority of what promised was. They also didn't deliver on time (the game was once delayed) … and the result, is by far worse than original Warcraft 3. Initial release not having playable Prologue without patch, is one of the worst launches I have ever seen.
What is behind this? I don't know, is Blizzard having problems with low revenue and being desperate? Did their talents left? Is their management that dumb? Etc. It can be anything, or combination.
Main thing is - they're not the company they used to be anymore.