I think that’s the influence of other YouTubers: he’s hanging out with the Safety Third guys, who are (as their name implies) trying to fast-run a Darwin prize. They make entertaining science-y stuff. He’s also hanging out with Mr. Beast, aka Jimmy Donaldson, which I suspect is why Mark is less fun: Jimmy has this extreme discipline of optimizing videos for views that carve the authentic excitement out to stuff cliffhangers every second instead.
For example, Mark Rober’s previous projects, like the always-on-target dart board, are much better. He’s quite smug on this one, too, but that’s his screen persona: an over-confident Californian frat-ish dude turning into “the best” uncle. He talks about this offline; it’s his way of making childish pranks fit his adult frame.
If you like the dart-board one more but thought it was too prankish, you might like Shane Wighton of Stuff Made Here in the Pacific North West: he’s more earnest about how hard it is to make hardware. There are still the occasional pranks (and the over-confidence because he’s using a robot), but there are a lot more technical details. His on-screen persona with his wife (who claims, on screen, to hate all his ideas) is not very credible, but more grown-up than Mark Rober’s Nerf gun fights.
Otherwise, Destin Sandlin of Smarter Everyday is the actual fun uncle, a Southern engineer to the core and a lot more earnest on screen. Alec Watson of Technology Connections is a MidWestern fix-it-all, who cares far too much about old tech. And finally, Tech Ingredients is the real deal: New Englander, no messing around, projects that are genuinely breakthroughs, with enough detail to reproduce in your garage.