He's losing people because they prioritized advertising over connections. That's why people went to facebook, to connect with people they knew. Then it changed to algorithms that maximized the ads and peoples stopped caring.
Then the blockchain came along. Why would they stay there and let Mark profit when they could come here and get paid to post and connect with their friends? It doesn't make sense. I think they'll try to introduce blockchain and make a go of it, but I think they passed their peak.