I have been around some of the tech elite you’re referring to, and I propose that the disconnect arises because Silicon Valley uniquely revolves around Scale (how many people you can reach) and Impact (how big a dent you can leave in the universe). It’s impossible to overstate how ingrained it is in the culture, and it is very explicit when you talk to folks at Bill & Melinda Gates Foundation for example: the ability to measure and prove the impact of your project is as important as the project itself.
I admit to being a member of this culture, if not wealthy.
To me, the types of art you mention - art galleries and live theater being good examples - are extremely limited in serving relatively small populations concentrated in city centers where there already is a lot of culture. The generation that created the Internet is, for better or worse, much more interested in bigger investments that can reach everyone on the planet and hopefully improve lives in some measurable and long lasting way.
I’m sure the wealthy here in California contribute to the local arts community just like anywhere else. But there is no equivalent in the arts to curing polio worldwide or giving every child access to the Internet, so I don’t personally disagree with prioritizing these agendas in a coordinated way.