Because they are buying assets with debt just like everyone else, and they don't actually care about ROI via rents, either due to "appreciation" (really, further inflation), or they're expecting the financial system to collapse.
In reality, the economy has been booming for the "haves" and those people are the ones bidding up homes and pay $50k over asking with a 6.5% mortgage. Corporations don't care much for home rentals when treasuries are paying 5% with zero overhead and zero risk.
Sucks to be poor and sad to be poor and still eating the "evil corporations" delusion.
On a per house level, undocumented immigrants can often pay more than others because they are willing to live many more people to a house with rents being charged on a per-person basis. If the house is all male workers, homeowners can charge $100 per week per person (now, it used to be $50 and before than it was $25) and can have up to 4 people per bedroom and often multiple in the living-room. If families, there can often be 3-4 families in a single house, all paying less than they normally would to rent an individual house but much more total than the house would ever rent for otherwise.
While I bear zero animus towards immigrants, this seems obtuse. Why are those companies willing to pay so much? Because they predict they can charge enough rent to make it profitable anyway. Why would they think that? Because immigrants can compete down at the level of rents.
This seems like the same mistake people make about "luxury housing," but on the other end of the market. Building housing at the top of the market does indeed make things cheaper at the bottom of the market, and bringing in people at the bottom of the market does indeed make things more expensive at the top.