I mean, there were people who might as well have put crank engagement on their CV as full time job experience. But every once in a while people who did not really have that as a hobby would spot something interesting amidst the crankery and exposit something. I think TT was in the latter category.
There's a lot of hours in a day, and TT is very quick, so it's not out of the question that he wastes a lot of time online. Anecdotal evidence from his Princeton days, the speed at which he types his blog posts, and the large number of links on his website indicate that he likely spends an inordinate amount of time online. Other very productive people like WS and EG are also no strangers to excessive consumption of online content.
These are all blasts from the distant past, take my recollections with a grain of salt. I think he was mainly a compulsive NetHack player, had to modulate it after his famous quals experience, did indeed consume a lot of online content .... but Usenet played a minor role in the grand scheme of his time-wasting. He wasn't one of the people who were invested in the specific flamewars or anything though he probably read most of them.