We're talking about how he got to that point where he felt the need to kill his parents, we're not talking about what he became in the end. He wasn't always mentally ill and to imply that would be naive. Furthermore I would say that most mentally ill people and drug addicts don't kill their parents. This is an extremely rare occurance
This is not what we're talking about at all though. He spent most of his teenage years homeless or on rehab. How many kids you know that are homeless in their teenage years and why you don't think that will have some severe mental impact on a kid still growing up? This is not a good upbringing, I don't care if his parents had quadrlillion dollars.
This is simply not the truth at all given what we know. He was sent to rehab at age 14 and spent the vast majority of his teenage years in rehabs and other therapy boot camps. How is that enabling him? He also by his own words wasn't sent for anything serious but for using antidepressants and smoking pot. He himself only started cocaine and heroin on the advise of other drug addicts he met in rehab. Now you might not choose to believe him, and that is fine, but I myself choose to because he was pretty forthcoming about himself in the Dopey podcast. And as of right now it's the only version we have to go on.
He was off and on homeless or living in hotels and only came back living at home because he agreed to his parents demands that he go through another rehab, therapies, medicine, etc. They never 'appeased' him unless your idea of appeasement was that they completely cut him off everything and let him rot on the streets which I think very few parents would ever do that to their child. And depending on whether he had an inheritance from his grandfather, I don't think they were ever capable of cutting him off. I doubt he brought drugs and other stuff by using their money after all.