Convenience concentrates, by default
Liquid staking is convenient precisely because it abstracts away validator operations, users don't need to run their own infrastructure, they just deposit tokens and receive an LST. But that convenience has a natural side effect: it's easier for users to deposit with one or a handful of well-known, trusted liquid staking protocols than to research and choose among many independent validators themselves. Over time, this can result in a small number of liquid staking protocols controlling a disproportionately large share of a network's total staked capital, simply because that's where the deposits concentrated.
This isn't a hypothetical edge case, it's a fairly direct consequence of how liquid staking is designed to reduce friction. The same qualities that make a protocol attractive to depositors, brand trust, deep integration across DeFi, a reliably pegged LST, are the same qualities that make deposits concentrate there rather than spreading evenly across many smaller validator operators. The more convenient and trusted a protocol becomes, the more stake it tends to accumulate, and the more stake it accumulates, the more convenient and trusted it looks to the next depositor.