Power of the Guardians wouldn't activate?

I can't complain too much since Power of the Guardians is so OP, but not sure why they didn't work in this scenario.

I had a monster with 2 PotG equipped, each with 1 spell counter and then my opponent played Successor Soul, destroying my monster without any prompt to activate my PotG effect. As far as I understand, this would be considered "destroyed by card effect" and my PotG effect should have been able to activate? Is this just a Konami oversight or is there some else I missed?

Log included, no other face up cards or effects would have been limiting/negating my spells. Just trying to understand what happened.