I got the impression that Redmond's sobriety was key in how the trustees could give him money. He is an adult and no one can truly control what he does with the money, but I think she tried to do whatever she could to require him to stay sober and drug free if he wants the money.
you can control your money after death through a trust however you please for the most part... happens all the time, age is just the usual factor for releasing control of the money.