I mean, they are so rich, they can start to mine Bitcoin, even if they lose some money they shouldn't care, they are ok with all those money they already have.
Am I wrong?
If you became rich and you are doing the dream life that everyone wants is thanks to Bitcoin, don't let him die.
You can only speculate that they have sold a lot of bitcoins, cause if that's not the case, their actions goes against logics.
However, don't forget that we have very talented people doing a good job improving Bitcoin, like Adam Back, core developers and people building stuff to the ecosystem.