However, it could also be that given the quick rise in cyber warfare that they do not want to be caught in the crossfire and carrying and dealing with the loads of DDOS and pure hacking attempts going in both directions.
The burden of dealing with this as well as payment issues and maybe for purely ethical issues of dealing with a proven lying dictatorship may have been the full motivation.
This again is a slippery , and dangerous slope.
Every network carries traffic that somebody somewhere finds 'objectionable'. If providers start making their own determinations about what is and isn't 'ok', it's a road to massive segmentation and separation of the internet. Already a road some countries have been going down, which is bad enough.
( I am not implying that this is why Cogent made the choice they did.)