Every exec at FB is compensated via share price. So yeah, they've all taken a massive hit to their comp. Zuck is down 100 billion YTD.
And so it's not wasted money on Musk's part, it's spent for a purpose, to seize control of what seems to be the most connected social media phenomenon out there. Facebook had to be weaponized through Cambridge Analytica and it wasn't meant to be public-facing knowledge. At this stage apparently that doesn't matter anymore.
That or it's megalomanaical overreach. Which is possible :)