A state can justify and sustain higher taxes on the wealthy by offering government services which indirectly benefit the wealthy (the externalities you mention). But it doesn’t follow that an arbitrarily poorly-ran government can sustain arbitrarily high taxes on the wealthy.

There’s some manifold of Pareto-optimal solutions to the problem of taxes and services.

California, for example, spends a lot of money to get not-great public schools, and has housing costs that are out of control. So if you’re importing new hires from other states, and pay them a lot to live here, and personally pay high taxes on top of that… that doesn’t seem like a Pareto-optimal point.

At some point, the wealthy will decide to move someplace that looks more Pareto-optimal. Better externalities, lower taxes, or both.