Who, exactly, is "huge" these days though?
I mean, you can just redefine anyone up and down.
I think you suggested box office was the best measure previously. By that logic, Samuel L. Jackson is the biggest movie star in the world. Which is a cute idea but come on.
The figures in this chart represent the total amount of worldwide revenue generated by all the movies a star has had a leading role in over their lifetime.
www.the-numbers.com
Whereas actual megastar Tom Cruise languishes at #8, and Jeremy bloody Renner is a bigger star than Harrison Ford. Don Cheadle is nearly on-par with Will Smith! Ryan Reynolds is barely above Pom Klementieff, who I daresay most people wouldn't even know by name (she's Mantis is the GotG movies).
Yeah because he's not really interested in appearing in drivel, post-Star Wars. There are some actors of his calibre who will appear in absolutely any trash if you just pay them enough, and respect to them (hello Michael Caine, Samuel L.), but Driver clearly isn't one of them.
How, exactly, are you determining that? Hollywood uses the term "unknown" pretty specifically, so I suggest you find a different term because using "unknown" in the context of Hollywood actors to mean something different to how Hollywood uses it is... unhelpful.