You could literally surround the PE mobile home park with new, available lots. But as the article states, it is prohibitively expensive for these current "mobile" home owners to move-- their abodes are no longer mobile in any practical sense. And, as the article also states, many have porches and other bespoke add-ons-- dismantling and rebuilding would add even more thousands.
This should be obvious on the face of it-- if those homes were truly mobile, like campers, the camper owners would just scoot (as camper owners do) when PE tried to jack up the rent.
I'll go further and speculate that a sizable portion of the owners are fixed income with very little savings. You could even offer free lots 500 feet down the road and some still couldn't take you up on it (at least without racking up some seriously predatory CC or other debt). No doubt these PE firms had a firm grasp on the owners income levels, home ages/prices, and all kinds of other data before they bought up the lots and jacked up the rents.
Unless your grand plan to flood the market with mobile home lots includes a "let's teach the users" campaign to tell everyone in the next generation to buy campers instead of mobile homes, adding supply won't help them, either.
Edit: formatting, clarification