The existence of Devil Fruits is deeply intertwined with One Piece lore. It’s one of the major elements constituting the series’ power structure, as well as one of the manga’s major hooks.
The series has long explained the different kinds of Devil Fruits, as well as the powers they grant to whoever is lucky enough to consume them. However, only after the time skip were they further explored, specifically the Devil Fruit awakening.
While Devil Fruits are already rare by themselves, those who can awaken them and use them to their full potential are even rarer, as it depends on how skilled and trained the user is on their Devil Fruit.
In Wano, Kaido said that Awakening occurs when your mind catches up to your Devil Fruit, and while that is a description, it’s still pretty vague in my opinion.
However, in the most recent chapter Vegapunk talks about how Devil Fruits are born from wishes, so likely the wish to be free or something like that created the Nika fruit.
Now here’s my theory:
For you to awaken your Devil Fruit, you need to embody the original wish that created the fruit, or at the very least understand it. Luffy couldn’t awaken his Devil Fruit until he truly desired to be a liberator, dreading the future of the people of Wano under Kaido’s rule if he lost.
Looking at Law’s and Kidd’s awakenings. Ope Ope was created from the dream to be able to perform impossible operations and Law being a doctor fits perfectly. Kidd has the power of being a magnet which was probably created from the dream of easily manipulating iron and steel, which Kidd is quite good at.
This could also explain why awakening Zoans is so dangerous, as wanting to become an Animal will regress your mind if not careful.
Theory by nicentra (https://www.reddit.com/user/nicentra)