I would not consider those an apples-to-apples comparison, neither RU or PRC has built a modern NB airliner. In the west a startup can just contract for needed expertise, they don't have to try to re-invent the wheel (or steal it).

I'm pretty sure their game-plan has been collaboration (or perhaps acquisition) all along.

Business plan: The big guys would have trouble selling the expense of such an R&D program to their BoD and investors. So get some VC to fund it, build something plausible and then the IP has value to traditional airframe mfgs.

If they pull it off, they can perhaps settle in as a bleeding-edge design bureau, kind of like Scaled Composites. Or sell the shop to one of the bigs.

What is actually different today is the development philosophy, enabled by very advanced computer tools, where production and mx are baked into the design from the beginning. In the old days you'd design the plane, fly prototypes, and then figure out how and if you could build (and mx) it in a cost-effective manner. Today they can in theory answer all of those questions on the digital drawing board. This is what the USAF is doing with the B-21, they are expecting the prototype to essentially be a production plane and very quickly ramp up from flight test to production. They took their time getting the design right, we'll see how it all works out.