All of what you've said, I agree with if it's about the consistency of the team and as well as the bettor. But I beg to disagree about luck is the main role here.
In sports betting, we've got stats to based with and that's how the bettors are looking up to if they are going to bet seriously.
While I don't dispose and ignore the factor of luck, it's not the main thing that brings up a win for both bettors and teams.
We can see a team with a lot of star players but lose from a team without a single star players. So, from this we can say the team with start players is unlucky because lose from mediocre team. I know, stats give us more perspective to choose one of team to bet on. But, this still a prediction with higher probability to get the right choise. But, the results of the game, we never know before full time happens. So, there still a luck for us to get the win, well i aggree this cant be said as the main role for sport betting, but luck still become something that never be forgotten when we are betting.
In most sports, even with star players, that doesn't guarantee them to win. They have a upperhand but it still means that they can lose.
So, it all still goes with skills but I won't deny that there's a bit of luck in there. I wouldn't belittle those teams that have little to no stars.
They won't be inside the league of that sport if they are not good and skilled enough.