Ooooooh, a conspiracy theory thread! I like 
Personally, I… Sort of understand it, but it doesn’t make me any less salty. WP forums were just a minor add-on to the website. The vast majority of users never visited them, so it was a relatively small, tight-knit community. Using server power just to sustain it doesn’t seem very profitable. (This is largely WattPad’s fault, though - they made the forums a completely separate system from the main website. Ever since then, the interest began to die.)
On top of that, WP forums were always something of a festering boil. People went there to vent out their frustrations with the website, making it a hub of dissent. But also, people fought a lot, over anything and everything. It wasn’t the most toxic place, but forum users have strong opinions on everything - yet were very easy to insult. Add no professional moderation (only community volunteer mods) and you have a recipe for a disaster.
As you imagine, managing the place was hard at the best times. I’m not surprised WP CEOs decided it’s not worth money and effort. Suffice to say, though, it was a straw that broke the camel’s back for many people. There was a real exodus of WP users after the forums closed, many of whom moved straight to Tapas. This says a lot about what people think of it 