that was a high decision for facebook to joining in crypto investment, but well mark is a open minded people and take a step double from other people, so if they are trying to put in any stuff in the btc, they moving progress underground and make it all silent after all
Well in my opinion, Mark does not need to earn in Bitcoin and has already achieved great wealth but his intention to step in to Bitcoin is just to promote the crypto and to let the people know the hidden facts about Bitcoin that common people do not know. Facebook is an easy way and people all over the world are using it so this will in fact spread and advertise Bitcoin and the demand will rise for the crypto.