The trouble is, that probably isn't true. They might have had nothing without him before, but now they have 16 people left without him, and presumably by now some of those other people are technical as well.
So, his relative importance may already have been reduced from "indispensable" to "valuable technical leader", and his personal negotiating position is getting weaker all the time as the business grows. He may have to give up something of value now to consolidate his position for the long term, but if he's been suckered already then consolidation may be the best course of action that is still available to him. Of course even a somewhat reduced but secured stake in the business may still work out very lucrative if the company is successful at its new scale and funding. The real question is how much influence he has left to give up as little as possible while securing the rest.
The trouble is, that probably isn't true. They might have had nothing without him before, but now they have 16 people left without him, and presumably by now some of those other people are technical as well.
So, his relative importance may already have been reduced from "indispensable" to "valuable technical leader", and his personal negotiating position is getting weaker all the time as the business grows. He may have to give up something of value now to consolidate his position for the long term, but if he's been suckered already then consolidation may be the best course of action that is still available to him. Of course even a somewhat reduced but secured stake in the business may still work out very lucrative if the company is successful at its new scale and funding. The real question is how much influence he has left to give up as little as possible while securing the rest.