While I 100% believe a shitty company would do this if it benefitted them, I just don’t see how SL warrants the effort. It doesn’t make enough to be sexy to pillaging. All its tech and assets are outdated. Its not really a serious competitor for...well, anything. Honestly, it’s cheaper just to let LL continue to mismanage it into complete oblivion.
Pragmatically:
SL may not be a direct competitor for anything Facebook, or any modern company, is doing right now on a technical level.
However SL's user base, regardless of its size, is still attractive because it represents a large group of people who are 1) known for sure to be keenly interested in using a virtual world and 2) proven to be willing to spend LOOOOOOOOOOTS of money, consistently over time, as part of being in that virtual world**.
Thing is, as long as Second Life is still around, most SL users are satisfied enough with it that they're not going to go anywhere else. If SL actually goes away though, a lot of its userbase will need/want to go
somewhere to carry on. I know some might say they would just quit virtual worlding altogether if they couldn't find a 1-to-1 replacement for SL, but I don't think most of its users would.
**There are nuances, yeah I know that, but other companies probably will not understand them or simply won't care. Silly things like nuances certainly wouldn't stop Faceborg from trying to suck up and squish SL if they decided they want its customers for themselves.