Why do they accept the lock-in?

Looks like there is no good answer if we view them as one entity which could simply make up it's mind. But it's a bunch of individuals, who probably disagree at least over details. Some probably have individual ambitions or pressures, some may struggle to pay their bills or satisfy their family or even themselves.

And for each individual on the fence, it's always an advantage to still publish to the network while hoping the rest of the group abstains and establishes a better platform in the meantime. Would you risk publishing your finally successful hard work to an immature platform, where it might not receive the attention it deserves?

And because they're smart, they know everyone else is thinking the same. Now we have reasonable doubts in something which relies on trust.

Basically, game theory. The system will find it's Nash equilibrium at a point where every individual move will worsen that individual's standing.

To break this spell, you need agreements and contracts. Someone needs to work on that, negotiate and lobby for it. But who? Would anyone who would benefit from that step away from their actual work and work on that meta-system instead? Would anyone who would not benefit from that system work on it? Maybe this could be a research project for scientists who already study these topics. Otherwise, I don't know.