"Do surprisingly well" depends on your expectations I guess. Yes, it can be a treat to see a healthy herd. It's much less a treat to see emaciated, dehydrated horses, which are not that uncommon:
and while one can argue about the "true" motivations of the people arguing for culling/control, it's absolute true that conservation organizations think that feral horses are bad for the environment:
Wild horses in North America are a very interesting question.
All equids evolved in North America. For tens of millions of years they were here, and only have been gone for ~10,000 years until being reintroduced by the spanish. [1]
[1] See the fantastic book "Twilight of the Mammoths"
https://stateline.org/2022/07/20/westerners-struggle-to-mana...
and while one can argue about the "true" motivations of the people arguing for culling/control, it's absolute true that conservation organizations think that feral horses are bad for the environment:
https://wildlife.org/wp-content/uploads/2017/05/FactSheet-Ho...