Please, do not mix up the disabling and problematic Preoccupation with the “normal” autistic way of having a hobby/interest.
See Preoccupation as self-medication for extreme stress/anxiety and treat it the same way, help with solving the causes, leave it if you can’t and it is per definition like any drug bad for the sufferer in the end.
For quite some time I ‘m working with professional (mental) aid providers, and a number of things come up again and again