I count more software that has been ruined and/or killed by acquisitions than the one bred by those.
One off the top my head is Google Docs[1] which, for the longest time, I was pretty sure it was in-house tech. It's actually a number of acquisitions for the collaborative editor tech and then MS Office support.
It seems now that most incumbents have enough cash to not care about being that strategic about acquisitions.
"Have you heard about Figma?"
It's a market efficiency, I guess, otherwise they'd stick with the R&D approach.
I think the Golden Age of internal R&D was probably 1960-1980 at Bell Labs, IBM and the really large engineering cos like Boeing?