I am playing the devil’s advocate and writing that the main issue is materials materials materials, ala Steve Ballmer’s developers developers developers?! So that all these five startups seem just ancillary or toooooo long a shot (imho).
There is also a question of costs: for deep space missions, beyond LEO you need real rad-hardened electronics. Rad-hardened electronics exists. Cheap rad-hardened electronics doesn't. And there is pleny of other examples. Ion engines is mature enough technology. Cheap ion engines on the other side...
You need to use materials to make something, and that thing needs to fulfil a purpose. But until you have an objective and try to make the thing and work out what the thing is, you don’t even know what your requirements are. That’s why engineering projects like Apollo and the shuttle drove materials science advances.
If you put the materials first you run the risk of creating a carbon fibre composites company to make giant space rocket hulls, just as the people actually making the rockets decided for their project they’d use steel.