I gathered from the article that the main reason people were moving was because of the high cost of living. Higher taxes certainly are a part of the high cost of living. However, clearly the high cost of housing is the largest contributor to the high cost of living, not taxes.

One could easily think that taxes in California are too high, but that in the place one moved to they are too low (assuming they are substantially lower than California of course). So I'm not convinced there's an inconsistency.

Personally, I think US+California taxes are too low, especially for high incomes. But I'm undoubtably biased from having grown up in that well-known-haven of high tax rates called Switzerland.