Ratchet killed them all?
I use to think this. But then realised you only kill about 30 Cragmites, so that's hardly an army :P
Do we know how many cragmites came through? If it was me I'd let a few through, make sure they supported me, then let the rest through. Thereby ensuring I was in command. So maybe only an elite 30 odd came through. Otherwise, I reckon they were banished, contained, imprisoned etc.
Well Tachyon did say on Fastoon (or Igliak?) "Once I have gotten my entire family through the portal-" something something. I don't have time for rmembering quotes right now I'm on holiday!
My point is, you may be right. But it would seem wierd that by the time you've been between three planets Tachyon wouldn't have gotten eveyone through yet.
I'm on holiday too!… Heck!.. everyone is on holiday here in NZ for now, lol
But anyway, I reckon that the Cragmites were banished back to Reepor, only one way to find out! revisit planet Reepor! … then you find a whole army or Cragmites but yeah, that can be the only reasonable explanation…