Well in my opinion the reason for that winrate is in the simple mechanics of his kit.
Regardless of his early game trades or laning presence, Wukong has an incredibly powerful teamfighting combo. The combination of his short-range stealth and jump allow him to position himself wherever he needs to in the fight (unless you are lucky enough to catch him approaching on a ward and then you might be able to catch him out) and then his ultimate goes off.
Oh boy that ultimate...
Let's look at it mathematically
Ultimate = the channeled damage of
ultimate + the AOE pop up of
ultimate - the ability to interrupt said channeled damage.
This...to me...seems profoundly unfair.
If it behaved like most powerful ultimates of this class then people like
or
would have no problem cc'ing him to survive (which is what makes it okay that people like katarina do so much damage on their channeled AOE ablitlies). This creates a fun skill contest as the channeled ultimate tries to go off in a scenario where it cannot be cc'd and then is able to devastate the fight.
Wukong's ultimate, however, simply ignores this dynamic and dominates every fight instead. Not only does it ignore cc, it actually provides cc of it's own so that you can't even escape it (the other way to counter powerful channeled abilities.
TL:DR
Wukong is powerful because of a fundamentally flawed kit that includes all of the strengths and none of the weaknesses of similar abilities.