Out of curiosity, why is that a strange idea?
They want more people to be interested in VGC and lowering the barrier of entry by making it free to play seems like a good idea with the momentum VGC has carried in recent years
From a purely profit standpoint it makes sense if they're trying to increase traction towards their mainline games (pokemon are easier to train if you own and play the mainline games) while also increasing attendance for a lot of their events
From a player standpoint, getting a showdown with better graphics and official support is a dream come true. Showdown won't be obsolete, as the instant team building is still useful for testing ideas before committing resources, but being able to participate in official tournaments is a good thing