Probably in part that it's irrelevant to most console and PC gamers. People are probably hoping to see some good old IP's brought back to life instead of laying between Bobby's cheeks and rot, and the only chance they are seeing is if Activision isn't in control of them anymore.
Activision Blizzard is a mobile company, out earning PC and consoles combined. Blizzard is a shell of its former self, and Activision don't know how to make anything but CoD, remake and a rare Crash game.
TLDR: Most people don't care too much about this merger, and let's be honest, the Zenimax one was more relevant to most people here.
I doubt this deal will be bad for the consumers long term or short term. The mobile market is so f'ing massive that this deal won't change shit for them, as MS footprint in that part of the gaming space is tiny.
And for consoles, (even if they made CoD exclusive), it would probably just spice the competition up a bit. Making it more fierce. For PC, it's pretty much completely irrelevant. Both MS and ActiBlizz already focus on PC.
Currently, Activision is a CoD factory, and that is all they give a shit about within the console and PC space. Mobile is too big(Remember that mobile is 50% of everything Activision Blizzard is). Blizzard is.. not so much the giant from the past. They are releasing a game as often as MS is releasing an OS, and the quality of what they release is not exactly top-notch, Diablo 4 came out to pretty good reviews, while users said: eh... this isn't what we wanted as time goes.
At the end of the day, I feel this is MS throwing away a massive part of their war chest on mobile garbage. (from a PC player perspective), but on the upside, I might get to see some Hexen or Soldier of Fortune in the future. And if I don't, well, nothing has changed, as it's just rotting between those ass cheeks I mentioned earlier.