Investment companies own only about 2% of the housing market, and most of these are rented out. Investment companies aren't really the cause of housing prices remaining high - in moderate- and high-demand areas, we simply aren't building enough to keep up with demand.

Investing in housing only makes sense when supply is limited. The way to stop investors from hoarding housing is to make housing a bad investment by building a lot of it so cornering the market is impossible.

Except they cannot increase rents when there is enough supply for a market to actually work.

land value tax would fix this

You literally didn't read the article.

Build more housing.