IME anyone who runs into a situation like OP did where they genuinely want to help get the horses out of a bad situation, it works best when you ask for the horses as a gift instead of offering to take them.
When you offer to take them off somebody’s hands as a favor to them (even though that’s clearly what it is) it can make the owner feel like a failure and they can take it as a dig that somebody is saying they have failed their animals. There’s a lot of shame around surrendering an animal and there should not be.
Instead, I would just say “hey can you give me this horse”? /“I really need a pasture mare”/ “I’ve always liked this horse”/ “giving him to me would mean so much”/ “I need a babysitter” etc. This way the owner feels like they are the one doing YOU the favor because they are graciously gifting you this horse and therefore not a failure. This just takes the shame out of the equation and coddles their ego which can be an effective way to get what you want.