Hmm… how about Tachyon referring Ratchet as the "last Lombax alive"? Angela was a Lombax too, and she also lives in Solana! Was it because the game was really a remake, Tachyon not able to track her, Angela already dead, or he's just too idiotic to think there was only one Lombax left in the universe?
I think TJ didn't just think it through that much… Don't forget about Azimuth. He was living in Polaris all that time, a lot of people knew about him (Fongoids, Vullards, Vorselon), yet somehow Tachyon didn't go after him. He can travel to a different galaxy and invade it's biggest city yet doesn't bother visiting a junkyard planet he himself controls? I wouldn't say he's an idiot, he's just a victim of plot holes.