More were lesser gods than demigods.The ones who were deities were basically demigods, the weakest sort.
Except that they would not. The odds would clearly favor the higher tier deity, but there would still be a significant risk that the lower tier deity wins, and in any case the winner would be pretty spend from the battle and that could make them tempting prey for other deities.The intermediates and greater gods would have beaten them like they were 2 year olds had they fought. The lesser gods would have done the same to the demon lords who were demigods or lower.
A lesser power needs to carefully consider whether fighting a demigod is truly worth it. Even if she has an 80% chance of winning, that's still a 20% chance of losing everything and even if the 80% chance comes true, can she quickly enough recover from her wounds and consolidate her gains bevor a rival attacks?
Kiaranshalee was a demigoddess when she fought and killed the lesser god (back in the day) Orcus.
The chances grow and the risk of injuries decline the bigger the difference in divine tier, but even greaters slaying lessers need to be wary about the power they have to spend on that and the bloody nose they might suffer in return, even if the risk of death is very, very low in such a match