The thing about money is that you don't need to be successful if you have enough of it. The job of a heir(ess) is to live long enough to inherit and not get disowned.

Granted there are a few cases where even money can't save someone. A severe schizophrenic for instance could have poor quality of life even if they receive top quality care and have a trust fund. Technically they are better off than if they were poor and had it but the good is greatly reduced.