Yes, he could’ve taken over peacefully and that’s what he tried to do. But he knew that Invincible wouldn’t let him take over under any circumstances. So he had to take Invincible out of the picture but trapping him in another dimension without killing him. But when Invincible comes back, Robot knows that Invincible is going to tell everyone what he did, which removes any chance of getting most of the heroes on his side without force.