That's a reasonable explanation. Desperate times require desperate solutions; I have my doubts they were eager to start sacrificing from other places.

[Silco had been around enough people to understand unstated subtext better than most, and he had seen enough weird powers since coming to this place that he assumed that he was one of the odd ones out when it came to being vastly underpowered. It seemed to him that most of those screaming off to the island had thought themselves powerful enough to make a difference - and actually hadn't - so it was less about power and more about strategy as far as he was concerned.

He made a non-committal gesture with a hand.]

It seems to me that many who have the strength and the ability to potentially make a difference in the Rumpiturian's lives likely won't.