I keep saying it, when a company gets bought out, that's usually it. In many cases, their fire ain't the same any more. Especially when they're an older company.
The cats who were working there initially get paid and dip. Now you're left with a skeleton company where all the innovation that was once there are now gone and you just got a bunch of new faces without the gift that made the company great.
You can hire a lot of new, young talent but that doesn't mean they're gifted to carry, like the people who made the magic were. A lot of young physicists are smarter and even have a higher IQ than Albert Einstein, but they ain't Albert Einstein and will never come up with anything nearly as significant of contributions. Chances are you see a lot of these people everyday on a lunch break. Every well-known big company has ultra-smart geniuses working there. Genuises aren't rare, but legends are.
The shyt these companies pulled off to go to the next level are basically a timestamp of catching lightning in a bottle at the right place, right time - simply conditions very difficult to replicate. You can't buy nor pay for that.
Even if you have a new talent they're going to have a hard time climbing the well-established hierarchy at said company and usually end up dipping to another company where they can see their contributions have more weight and less resistance. Problem and risk is, if you do believe in their talent, spend resources to back them up but are wrong - that's a large amount of time and money going to waste and you've basically pissed off the experienced older people there.
At the end of the day, these were really expensive acquisitions for Microsoft knowing the main talent of the companies are older (and some central to their prime like John Carmack and Zenimax were long gone) and times aren't the same.
PREACH