Marlinspike is the CEO of Signal Messenger LLC, and he also coincidentally believes that people shouldn't make clients which are compatible with the official Signal messenger (even though the protocol and code are freely available), and shouldn't even try to distribute Signal from app stores that he doesn't approve of.[0]
I don't actually know if he receives a meaningful salary from his CEO role, but Upton Sinclair's adage still seems relevant for explaining Marlinspike's views on decentralization: “It is difficult to get a man to understand something, when his salary depends on his not understanding it.”[1]
It's also worth pointing out that non-official Signal clients would be less likely to include support for MobileCoin, which "gained over 450% [in value] since" Signal announced support for it.[2]
As for why Marlinspike might have abandoned the goal of decentralization, I think Upton Sinclair might have some insight.