A bunch of reason
1. Relentless seems to prefer land defense over sea defense
2. Relentless' daily battles will UF limited their bierme numbers
3. Triad hasn't really been fighting (as far as I can tell) anyone lately so it would make sense for them to have a lot of biermes and alot of people willing to donate
4. Triad had one siege to spread their biermes over and relentless had to defend against UF attacks and sieges
To be honest I think triad is the only alliance capable of such high bierme numbers in a single seige at the moment
UF have 4,252 cities. All things considered, even if amazingly only 500 of them were bir nukes, and each nuke was 300 birs( a little less than average), and even if 200 nukes were out doing something, 300x300= 9000 birs...So in my opinion it is just your excuse for players being selfish. I reckon you guys with the amount of cities you have you could have broken that siege if everyone tried
Your math is correct but those biermes and LS have many cities to be defending and attacking at once. Also the travel time to that ocean isn't the best and it would cost a great deal of troops. Saving one city just isn't worth that.