I've actually landed his Up-tilt more often than his Warlock Punch.
Can we PLEASE stop saying this, people? It's starting to annoy me.
The opponent screwing up is a possibility.
Mindgames are a thing.
Baiting is a thing.
Using perfect timing is a thing.
I land moves like Volcano Kick A LOT, and my opponents definitely weren't braindead.
How to put it...
No human player plays 100% perfectly at all times, but generally, there's circumstances that are easy to read for most and thus can be baited and/or punished when they occur. One of Ganondorf's biggest problems is that his combination of moveset and mobility leaves him with an extremely low margin for error- It's not hard to read an incoming attack from him. As a result, Ganondorf will very rarely be able to dictate the flow of the match, meaning that the way the battle pans out will be mostly left up to his opponent, putting him at a very severe disadvantage.
I sure said that!

Forward tilt.