It's sports entertainment and was also on Sky Sports. I'm guessing that you don't appreciate BT bagging the rights to one of Sky's crown jewels?? It'll will be a subscription driver for BT Sport and will bump up their overall viewing figures and make the BT TV product stronger as a whole.
WWE call themselves "sports entertainment" and have done so since the 90s. It's recognising that it's fixed, there are "storylines" and that it's not a genuine competition. But the sports element is still important in that it requires strength, athleticism, conditioning and technical ability.
Probably the best thing to compare it with is something like figure skating or professional dancing. The "competition" element comes from being the best at putting on a show.
So it's Strictly Come Dancing with attitude. I hope BT haven't bought up World of Sport Kent Walton's reruns!
At least it's not compulsory!