What usually happens in a 3 way FFA is one person sees they have the chance to destroy the other, and they try to do so. What they dont realize is that by focusing on a single player to destroy them they've handed over the game to the 3rd player, who then destroys you and cleans up the rest and wins, having spent the game relatively untouched.
For example in a recent game I was ina 3 way ffa with of of the bee and emil. Emil made the huge mistake of focusing on destroying me. So while I was being pummeled into submission, foe of the bee built up an army of warrior kbots, then marched them into emils base unhindered and destroyed emil with ease. Emil had bene focusing on me and as such he had an unsecured border with foe of the bee, and foe of the bee had not been attacked because I was defending against emil and emil was trying to destroy me.
So when Emil ahd bene utterly routed, foe sent down his armada of kbots into my base, still recoverign from emils prolonged attack.