The BC conservatives used to be the the BC liberals and BC conservatives, the BC liberals being the centrist middle of the road types. They were merged into the BC conservatives in a unite the right type movement as seen in Alberta, but not via party members voting for that, but largely by the leader who unilaterally decided to do so. Since then the leadership has gone from one maple maga quack, to a even bigger maple maga quack.
The newest maple maga quack won the leadership 51-49, and has taken that mandate to take full control of the party, swing its policies way to the right (She would make PP look slightly right of center by comparison) and refuses to listen to the BC liberals centrist types.
As such, and by virtue of not being in power like the UCP in Alberta, the Centrists have had enough and are now jumping ship.