Good questions.
I think he didn't really care and does not currently care about getting away with it. He felt cowmpelled to do it and while he did not want to be caught, it wasn't his top priority.
I think he wants the notoriety (he thinks academia awards fame and fortune, as that's what he's seen in some of his prior experiences, but in fact, it's just a long hard grind to get a public job as a criminologist - or an academic job; to my knowledge, there are no freelance criminologists who haven't already written books and sold scripts, etc).
I think he knew he'd caught and prepared for this phase of defending himself in advance.
Why? I have two theories. Either part of him realized he really needs to be caught and he's daring Society to catch him (meaning: he knows he can't control himself and that he's a monster, so we need to stop him).
OR, he is hoping merely for book deals and fame, as you suggest. Maybe both theories can be right at the same time.
I want to add that many criminals express some degree of relief at being contained and prevented from any further evil actions. This is usually only one of the things they tell themselves.
In a weird way, we're seeing a generational shift in how mass murder/potential serial killing works or gets set into motion. "You're okay, you're fine" as his mantra (if true) is not what Random Maniac Murderers were saying to themselves back in the 1950's, as far as I can tell. He's something like Attias or Rodger (and he knows this). It's not a suicide-by-cop situation, it's a "containment by state prison" kind of situation.