WWE aren't the boundless well of surprises they once were, and frankly, it's understandable.
There sits around a table a collection of creative minds frazzled beyond reason catering to the whims of an increasingly irritable old man, piling on to sneak lines of dialogue into a bloated three hour show that routinely neglects all narrative convention anyway. Writers don't seem to be allowed to work on their own programmes - passion projects with favoured performers - instead contributing the same voices to a host of different personas and angles that subsequently all look, sound and feel identical. If there was a heel turn worth its salt in 2018, it's likely it'd be diluted by another inferior one in the very next segment.
Done right, they provide a storyline with a spine. A raison d'être for a babyface beyond workplace bullying or obnoxious d*ckheadedness at the expense of an authority figure they've suddenly developed a dispute with. The logic of a turn inherently checks out too - corruption is often rewarded until comeuppance is sought and gained.
The most enjoyable are ordinarily those that come as a complete shock. A great babyface should make even the casual observer feel part of their journey, and thus feel the pain of a former friend's devastating turn.