Broken Star needs the AI players to get aggressive in order to keep the rebels from dominating. I see little sign that they buy good units and build up a decent army. Instead, they mostly turtle within their borders, skirmishing a little, and build settlers.
Which, BTW, cost so much that it isn't, usually, worth building settlers at all, since you can just take rebel cities.
Still, the rebel AI seems far too coordinated. While it takes them some time to get rolling, they are hard to stop. I thought I was doing OK, in my last game at Monarch (the orange eastern folks). I'd taken a couple cities and captured a nuke silo. Only to see the rebels take out one of the other AIs, and a succession of "20 turns to get the codes" messages about the rebels. So what, I have a nuke. I can't do anything to stop the AI from getting theirs (across the map). I'd be content if any AI could take them out, but they just sit at home and die. Another AI went down, before the nukes started to fly.
First rebel nuke was against me, and losing my capital pretty much ended my useful productivity. I could still pillage and buy, but my economy was toasted. The rebels, having taken down two AIs with just raw military, proceded to nuke and kill the others, before finishing off my last city. I'd captured another nuke silo, but it was too little too late. Even if I'd have gotten the nuke, blasting a rebel city is like shooting one elephant in a charging herd.
So, what doesn't the AI do? First, it never captures oil. Part of not capturing anything at all, but the only likely way to get that first oil city is to save cash (no research) and buy an army quick before the rebels build up. Second, it doesn't build up enough forces period before invading.
Now, because the rebels are essentially one huge nation, with loads of resources and airports for airlifts, they tend to blow away every player in potential power. Unless every AI goes after them and slows them down, their ability to concentrate defense forces and counterattack against the human. Your own success is your downfall, as the rebels go after you.
Position may matter. I think that my choice was bad. Two nukes close by, but the only oil city has lots of rebel cities to reinforce it. Maybe I should have taken down my nice neighbors, given that they were both less powerful -- easier to take down than the rebels -- and less than useful as allies. But I figured that would be out of character and unfair. My goal was to first defeat the rebels, and then dominate the other players.
If the rebels were less coordinated, and less capable of fielding large advanced armies (their production is way higher than all players combined), it would still be challenging and dangerous to take them on. As it is, you can get a few cities crushed before the rebels hit their stride, and then, how do you stop them from getting nukes and taking you out?