Not every purchase needs to be multi-billion dollar outlays. Hell, the Zenimax purchase is an outlier among outliers, there is no historic equivalent I believe in the industry.
The point is Sony are acquiring stuff, they are paying over a billion to AT&T for CrunchyRoll in cash. They aren't hurting for money, especially not on the Playstation side.
And no. MS don't care about internet chatter, they care about their bottom-line and shareholder value. They are spending big right now to bolster themselves for the fight against the other internet tech giants who have developed an interest in gaming as another vector for e-commerce and services.
Sony are not a threat to their ambitions because they are moving in a direction where rather than competing, their interests converge. Its pretty comical to me that there's a perception that Sony are a direct rival to MS whereas Nintendo are not, and people kinda go from there insofar as judging every move as a strike against the other.
Zenimax published on Nintendo too remember, bear that in mind.
Of course, MS care what is said on the forums and the internet. They didn't buy loads of development studios, look to make the most powerful console because of a discussion with the shareholders, so don't kid yourself on that one.
Forget about Zenimax MS allowed RARE to make games for Nintendo handhelds long after MS bought them out so spare us on that one. MS is playing hard to capture the market share dominated by SONY that's what it's playing hardball for
Nintendo hasn't bothered to compete in the High-end console AAA market since the GameCube