> Nothing about California's property tax decisions have anything to do with 99.9% of Zuck's (and others') wealth not being taxed!

That may be true, but you appear to have missed the part of the sentence you quoted that came after the semicolon:

  California reaches for exotic taxes because its normal one has been broken since 1978.

Because of Proposition 13, property tax increases in California will affect an extremely tiny slice of landowners, [0] so it must turn to other mechanisms when it needs more tax revenue.

In regards to private "wealth creation", it turns out that money is fungible and you absolutely can built a bunch of wealth off of a mortgage if the "market" value of that property has increased by a huge amount, but the costs of holding that property haven't increased much at all.

[0] This doesn't contradict what I've said, I've just left out some details. A quick summary:

Ignoring a few exceptions, when a property changes ownership its property tax is adjusted to be based on the current "market" rate. When nontrivial improvements are made to a property, the property tax is adjusted to account for the "market" value of only those improvements. [1] Some "clever" people have been known to get around the "property changes hands" trigger by making the property be owned by a company and distributing private shares in that company. Want out? Get rid of all of your shares. Want in? Get shares from someone who already has them, or maybe convince those who are in to make more for you. The property is still owned by the company, so its tax is not adjusted.

[1] It's important to note that repairs are not improvements. It's also important to note that the government can choose to ignore all of these rate-reset rules whenever it wants, as it did when all those extremely wealthy people in LA got their houses burned down in that big wildfire that hit LA.