Charls and Andrew were responsible for some of the more surreal/artsy/sharp content on early MDE and Sam hasn't been able to replicate their stuff ever since.
Here's some work Charls and Andrew did after they broke off contact with Sam:
https://youtu.be/rPmastvJfds
It's very surreal and skillfully edited, very nightmarish and dreamlike. Meanwhile Sam mostly publishes podcasts where he talks about cars or teams up with a few second rate crackhead youtubers with way worse editing skills. Without Charls and Andrew MDE can't exist, only the Sam hyde show.
TLDR: Charls and to an extent Andrew Ruse were very important parts of the MDE team and without them the writing and editing isn't as good. People want to know why they quit MDE because it's just not the same without them.
That's probably not why they're obsessed but it's why your average MDE fan talks about it 5 years later