If the population shrinks, their capital isn't worth much. Meta, Twitter, etc. all lose value when the user base shrinks, we've literally seen it already. If the population gets smaller by design, naturally this same thing would happen.

Amazon, Uber, owners of apartment complexes, commercial real estate titans, Fox News, etc. What do their powerful owners/managers do? Rupert Murdoch's family doesn't think "if only our viewership dropped by 90% we'd really be doing great!"

Elites are where they are because the current system has benefited them. They wouldn't want to risk that by shaking things up so dramatically.

All those things you described are proxies to control resources and produce security. The money, the attention, the influence etc. Yes, structurally those things become less important if there are fewer people.

But it doesn't matter! People are unpredictable and difficult. You don't meet most of them anyway!

You don't need to think about money in the same way anymore if you can produce the goods and services you need directly, using land, productive capital and robots that are approximately as capable as humans.