My impression is particularly for the over $5m group, a high percentage are wealthy foreigners from around the world buying through a shell company LLC. Folks from places like Russia, Middle East, certain African countries, China, etc. Wonder what that percentage is these days.
Hopefully, with the increased sanctions on Russia and focus on denied parties, real estate brokers and owners are actually doing some due diligence on who is buying rather than just selling blindly to the highest bidder.