I don't believe this is a money issue, almost all maintainers and big kernel contributors already work for big tech. Thing is, you can't just simply hire more maintainers as there are only so many senior kernel contributors around and most of those that aren't already maintainers probably don't want the role as it is now.
Sounds like a money thing. Being a kernel engineer is being handcuffed to one or a small number of companies and a particular community. Meanwhile going up the stack is easy, will pay the same or offer higher risk/reward financial choices and let's you work anywhere.