AI teamming up on me, wtf?!

So for a brief moment I had the most score, and then 3 AI opponents decided to gang up on me in ffa, and constantly raid me, even though i had bastion walls and a bunch of fortified outposts and a decent army they crushed me, whenever I destroyed 1 army another player would come with a huge army to overwhelm me, sometimes not even 30 seconds after i managed to fend off the current attacking army, literally the only reason why I am still alive is because of the maxed out natives i built in the trade outpost, however i can't build them at the speed the enemy shits out troops and at the speed the different AI-s attack. I am playing on moderate.