How is buying them a house, letting them live with you and supporting them making mistakes
It's making a mistake when it is done in order to exert overt, or covert control. When it is done to establish the power to both give and withdraw support based on the child's compliance with parental preferences/demands. When it is used to throw in somebody's face if they start to resist the response "how high?" when required to jump.
I cannot tell you if those were (conscious or sub conscious) motivations for the OP specifically. But they do exist prominently in the narrative of a specific sub set of estranged children and parents.
Those motivations feature in the accounts of the children who cut ties. Who recognise that what looked like generosity to the outside world was a form of attempted imprisonment into ongoing control and compliance. They talk about choosing to be free, regardless of economic impact, due to the increasingly unbearable drama and tension of trying to negotiate their parent's ongoing need to control them.
Those motivations also feature in the narrative of the estranged parents. There is typically a notable contrast in how specific elements get communicated to outsiders. The parent usually offers few, vague, minor and seemingly unjustifiable reasons for their child's decision to exit sharply from their lives. In contrast they tend to offer up more, and much more precisely detailed, examples of their economic support of the child who left. They offer a strong degree of clarity with regards to their generosity. A clarity they fail to match when explaining the motives for their child's departure. They tend to prioritise a focus that leaves the audience with the distinct impression they are unusually generous, and their child particularly ungrateful.
Have you ever heard of the saying "There's no such thing as a free lunch ?"
Within a sub set of estranged parents/children the strings on the not so free lunch are often one of the main reasons for the estrangement. In the sense that however nice the lunch, the strings of control are a significant element of the family's dysfunction. Eventually the need to escape that control becomes one of the primary reasons for a child's exit.
To outsiders who are more used to string-free, or more reasonably-stringed parental generosity it looks like cutting off your nose to spite your face. But for those of us who lived with far more onerous degrees of parental control, it looks more like taking a knife to the noose around your neck.
A vastly reduced standard of living, or an exchange for a lesser stringed lunch at a partner's parents' table, can feel like a small price to pay to breathe again.