If you're not familiar with academia you may not understand why tenure is such a big deal. It's a designation that generally is equated with "a job for life" or, more specifically, an imprimatur that the professor in question has met the high standards of their profession and has the "academic freedom" to research whatever the hell it is they think is important.
Tenure is a key vehicle for ensuring that our society has people who think about, research, and teach things that are unpopular. And getting there requires an academic track record of research that's accepted and vetted as important and high quality by an academic's colleagues at their own university, in their field outside their university, ad ultimately a series of gatekeepers at the department/college/university level have to sign off. It's the biggest possible deal for for an academic.
It's been a long road for Brian. This achievement marks a key juncture in a career that he's been building for--what?--fifteen years?
I'm happy as hell for him and proud as can be.