This is strategy that many are using. If you
see it - please warn people.
So basically what you do is you surround yourself with allies. Like a donut. Let them fight while you clean easy targets and bots. If ally dies- you take his provs FOR A CAUSE. Often they also ask for resources as they are the biggest, the strongest, with best chances to avenge you ( which rarely happens). They are the strongest cause they do not participate in wars and use that army as a leverage to swap sides in case their original coalition is losing badly.
But if miraculously donut survives there is a dilemma for a guy creating it. How to get rid of others without a fight. Either you send them onto expedition across the sea or throw them into war where they die. IN our case - there is nothing like that happening as I warned guys this could happen and to keep 50% of armies home. AS you see some donut fillings lose nerves and leave coalition deciding to go all out and take their chances of winning map using their own coalition as a chow-chow. But as i said - this is risky this is why they leave behind 1-2 people whom they offer provinces and 2nd.3rd places ....
Some people believe in that like Arrowhead and make a deal. Most of them will never see end of map. But it is in a good tone to leave at least 1 person from a donut alive so this person prize you as an excellent leader and commander helping people win a map. Good PR and all this stuff about other to make it till the end because it was very hard fight till the last day.
All to all you have classical example of a donut. I really hope it will backfire on the creator of it.
You have my advices how to defeat it, not lets get to fight.