There is a principle of Defensive Decentralization: when besieged, a well constructed decentralized system will further decentralize.
The corollary of which is: A well constructed decentralized system will identify & attack emergent centralization.
There has been a tendency for some decentralized systems to move towards centralization, even in non-adversarial conditions — most email going through Google servers, or a few Mastadon servers hosting a bulk of the users. The centralization isn’t always in-protocol, sometimes it can be political, in code, or in design — as seen in many blockchain projects. Designing systems that defend against this is an open problem.