Both skill and luck.
Daily trading of multiple coins executing orders based on your specific strategy using multiple market indicators earning steady profit slowly but surely requires skill.
Buying a coin expecting tiny return then suddenly shoots 100% due to huge pump by McAfee is luck.
Not always, but above imo are example of skill and luck.
Yes, a profitable day trading is always a combination of luck and skills because even how skillful we are but the market price is still not good then nothing profit happen, as the market value is always volatile because of the changes made by the traders itself and the investors and above all the big whales, therefore its all beyond our control.