It's a combination of both skill and luck. You can improve your chances of winning/making a profit through skills and experience but at the end of the day you still need some luck to win certain bets. I've had lots of instances where I only needed 1 goal/corner/yellow card to win my bet with just a couple minutes of the game remaining. Sometimes it hits,other times it loses, but I personally consider it luck since it's not in my control anymore and anything can happen.
If we talk about lotteries and slots, of course luck is the main factor, as well as games like poker and blackjack then skill is one of the factors for us to win, but if we talk about sports betting, I think our skills and expertise in analyzing the game are actually one of the factors for us to be able to make more accurate bets with an 80% guarantee of winning, And that's where the luck factor of 20% also plays an important role in every bet we make, so I think sports betting does involve a combination of skill and also luck, skill can help us to increase the chances of winning, as well as luck which is an important factor in every bet we make.