The "raid" itself was orchestrated by /pol/ and a few other boards that were sick of Tumblr's shit. They basically false-flagged against 4chan for weeks hoping to provoke Tumblr into a war they knew it couldn't win, which, Tumblr being Tumblr, it jumped at. Tumblr fought 4chan, immediately got triggered, and suddenly realized that they were fighting a foe that they couldn't shame and couldn't stop. It's very analogous to what happened when
Vade encountered the Kiwi Farms, only on a way bigger scale. Unfortunately for Tumblr, this was only the start. 4chan provocateurs chased the Tumblrettes to their safe spaces, found their preferred tags on Tumblr, started posting old favorites like Muddy Dicks
(that's not mud...) and Goatse. Tumblrettes deleted everything en masse and the "war" ended with a fucking slaughter.
Unfortunately, whilst this is widely regarded as
fucking hilarious, 4chan's modship at the time, increasingly pro-SocJus, was less than amused. This included prospective buyers interested in acquiring the site from m00t at the time, or so common chant goes. In response to the raid, 4chan tried to lock down /pol/ which had the predictable reaction of /pol/ immediately slipping containment and raising alarms - because whilst fucking everyone hates /pol/ - they're arguably the second-most despised board after /r9k/ - /pol/ occasionally lets nuggets of truth slip out when they're not claiming Jews are aiming a massive orbital doom-satellite at the USA in a diabolical plan to keep the McRib seasonal or whatever, and this proved to be the case when 4chan mods overreached in their attempt to slap /pol/'s shit.