You need the state to optimize sharing of resources

I don’t believe this to be true. There were no states in the earliest of tribes, yet they survived:

early human societies managed resources through communal efforts and mutual agreements without the need for a centralized authority. These tribes relied on shared cultural norms and direct cooperation among members to allocate and utilize resources effectively. The absence of a formal state did not prevent them from thriving. Instead, it fostered a sense of collective responsibility and interdependence. This demonstrates that resource sharing can be successfully managed through decentralized and community-driven approaches, challenging the notion that a state is essential for optimizing resource distribution.

you get smaller and smaller tribal groups competing

Over scarce resources - yes that is a plausible scenario indeed. That’s why a plan is essential in order for people to be able to believe in such an undertaking. The groups will need to federate on the level of neighborhoods, towns, cities, states, nationals, and eventually, the planet. If attained, that’s all the protection they’ll need. But granted, that’s a big if.