I think it all boils down to:
Are a band good live (that’s where/how they get fans)
Are the bands songs good/memorable
Does the recorded material do the band justice (does it sound like them, and live can they sound like it)
Are the band aware of the favoured format that said fans would like to buy their recorded material (if they want CDs, focus on vinyl at peril)
Are the band able to sell said recorded material both online and at gigs
For me if a band can’t manage all of the above, to get success it would have to be extremely fortunate. Getting all of the above still however doesn’t guarantee success.