Rhi's obsession with Disney is obviously her 'special interest' that many autistic people have. Apparently they are distinguished from a regular hobbies due to the duration and intensity of the interest.
Rhi has devoted an insane amount of the family's money, time and resources towards Disney. This must be seriously impacting their ability to do a wider range of activities or buy non Disney stuff as there is absolutely no way her channel is making anywhere enough money to cover the holidays, clothes, merch, Christmas decorations etc that she has bought. Virtually every aspect of their lives has now been influenced by Disney and she has encouraged her autistic kids to take on Disney as their special interest too so that she can say she does it all for them. This clearly isn't the case and the obsession with things like Disney bounding is clearly coming from her. There is absolutely no way the kids are insisting on wearing themed clothes that match the restaurant they are eating at everyday.
Some of the advice about managing special interests is around setting clear and consistent boundaries. Nobody is doing this for Rhi (probably because she would kick off if Neil dared to do this) so Disney will continue to dominate their lives.