>>645934939/news/ was deleted for being overrun with political bullshit, but they just shat up the rest of the site until moot gave them /pol/ hoping they'd at least do it with a sense of irony this time, then Hiro made /news/ again because politics brings pageviews and he doesn't care about quality.
/fur/ was deleted because obviously, but then Hiro made /trash/ because, again, pageviews.
/l/ was deleted because it invited too much CP.
I think all the other board deletions were just because nobody used them and it hasn't really happened since the text boards were purged in, what, 2013?