Are you sure they are the companies owning the homes? They look like realtors to me.
I have heard of rental funds buying up real estate but I think this is still a relatively small portion of the market with a relatively large number of players such as these
I’m not sure what that means, but if the link I gave was correct and the biggest one has ~85,000 homes, that’s only 0.1% of the total US single family housing market of 82 million single family homes. That would indicate that there would be thousands of landlords in most areas, meaning that collusion between them would require a sophisticated networked system between them.