I mean, if he invests in real estate he's buying that real estate from people who want or need to sell their property and would benefit from the sale in some way. He's not stealing from anyone by doing that. Sure he plans to make money but the funny thing about making money in a free market (I realize our market is far from free in many ways but the principle still applies) is that in order to do so, you must provide value to someone else. If he wants to buy homes that other people are selling, he's not hurting anyone by doing so. As far as those people are concerned, he's helping them out.

Now, an argument can be made that the bohemoth Blackrock, who owns every company in the stock market, shouldn't be allowed to go around buying up all of America's real estate to force us all to become renters, but frankly, antitrust laws, if it they were worth anything in this country, should be taking care of that. Blackrock has basically limitless funds to draw on and could actually buy up all the real estate in this country if they wanted to (and I think they do), but Bezos? Individual billionaires? They're small potatoes compared to the international bankers and the monopoly they run through their shell company, Blackrock, and its subsidiaries which we call the stock market.