Kind of a nitpick, but the CEO wasn’t a billionaire.

When you're earning $26M/year, it's just a matter of time.

A slumlord worth less than a million is arguably as morally wrong as a Blackstone CEO

From a very black-and-white "Bad thing is bad" perspective, sure. But there's a hierarchy of incentives and profits you're overlooking. The slumlord very likely carries their properties on some amount of credit, which means they're collecting rents on behalf of their lender. This lender, in turn, borrows money to increase their leverage and pays rents to a wealthier and more central lending authority. Eventually, the debts for all these loans get traced back to the major banks and other credit brokers, insurers, and private equity firms.

In a feudal sense, the slumlord is merely a plantation overseer and enforcer. The Blackstone CEO is the High Lord, standing on the backs of dozens of lesser aristocrats, who are themselves extracting wealth from their own plantation holdings, which all run thanks to legions of these slumlords going door to door every month to pound the rent out of their tenants.