It’s not really that deep - it’s a combination of network effect and inertia.
Because there’s “nobody” on Lemmy, people don’t join Lemmy. Because nobody is joining Lemmy, there’s “nobody” on Lemmy, and so on and so forth.
Furthermore, Reddit (and other big social medias) already have “everyone” there, so to the vast majority of people they’re just superior platforms as it’s easier to find both people and content. Moving to another platform means giving that up.
Debian 12 with KDE Plasma, works perfectly on every system I have thrown at it.