Maybe it's because I just don't care about Activision, but I don't see the big deal. Microsoft will leverage Activision as an exclusive studio? Okay? Every company has their exclusive studios. If I were Activision and I wanted this deal to go through, I'd just say "Well, we're not going to make any more Playstation games anyway". I don't think they can be compelled by the legal system to do so?
The problem is that Activision is a major publisher with 15 studios under its belt, not to mention all the IP. Just as a point of comparison, according to Google Sony has 19 studios currently under its PlayStation umbrella. Microsoft currently has 23 under Xbox. If Microsoft were to be allowed to purchase Activision, they would have literally almost double the number of studios Sony has. While that is nowhere near the record right now (that belongs to the Embracer Group at 131 studios), it's a considerable advantage.
According to the documentation Sony provided the UK Government, Call of Duty alone makes more money than all of Sony's 1st party studios' games in a given year combined, and by a significant margin. It's bad enough that Microsoft has been artificially propping up its failing Xbox division with profits from the PC division all these years without giving them an even more substantial financial advantage.
While I don't have hope that this will pan out, this acquisition absolutely should be stopped. Purchasing a studio or 2 is one thing, but allowing Microsoft to continue to simply buy its way into market dominance is absurd. Even more absurd is allowing it just because Microsoft has been utterly incompetent at managing their studios so far.