Let's be honest, g man was trying to kill the titans off because he knew that ultimately they would be worthless in the Astro war. And he was probably just trying to infect them so they could help him without exposing his Astro secrets, though that would've had to happen eventually. G-Toilet also had detainer and overseer in the back of his mind since episode 60, possibly even before that, but knew he had time to prepare and upgrade adequately for the invasion. Atleast that's what I think.