A "contract" where one party is clearly not of "sound mind" is supposed to be null and void according to basic principles of contract law[0]. Tricking an elderly person with dementia or a mentally handicapped person into selling their house for half of its fair market value is reasonably characterized as "theft" or "attempted theft".

The fact that a company is able to get away with stealing homes from elderly people who have dementia without these contracts being quickly voided as obviously fraudulent is all the evidence you need that the legal system is currently badly broken. These are not hard cases for a judge or a juror to consider.

[0]: https://www.law.cornell.edu/wex/sound_mind_and_memory