As I've said elsewhere, my theory is that Kaldur is a "The Light" clone who was substituted for the real Kaldur during Infiltrator. In the pilot the Light was going to clone the captured sidekicks, copy their memories, and replace them. I postulate that the cloning samples were not completely destroyed and that G-gnome who was in the Cave in YJ Issues #1 and #2 was a possible way that they got access to Kaldur's memories telepathically. I also postulate that clone-Kaldur is something like immune telepathically or a telepath himself and possibly a much more able sorcerer than original Kaldur. So he was not taken out telepathically in Bereft, he was faking, he did not put on the Fate Helmet (which is why he could take it off), that was faked. And he was not drawn in to M'gann's simulation (might have caused M'gann's simulation to go bad-- was it actually M'gann who is the most powerful telepath????) with the others which is which is why he sacrificed himself.
I re-watched Downtime. Boy, if you assume Kaldur is in the service of the Light, that is a VERY different episode.
The whole thing with Tula becomes an extended version of "I must step down as leader... Okay, I guess I can't." -- notice how "out of left field" that "I've decided to stay in Atlantis with you" is. Tula is certainly surprised and I would imagine so -- he had made his decision when he became Aqualad, why the change?
So if he wasn't back in Atlantis for Tula, why was he REALLY there? Well, look at the attack on Atlantis and remember the prison break. With every Light plan, the real goal is concealed behind a secondary, and more obvious goal. Breaking all the prisoners out of Belle Reeve would have been nice, but the REAL plan was to get Hugo Strange put in charge of the prison. The attack on Starro by Black Manta was the "prison break" part of the plan. What was the REAL plan. Prince Orm was left alone with Mera when Tula was unconscious and Tempest followed Aqualad. WHAT HAPPENED WITH ORM AND MERA -- WE DON'T KNOW. Clone-Aqualad went to see Black Manta by himself. But Garth didn't stay with Tula, he came along. When the two of them had a perfectly good disguise that let them get to Starro undetected, Clone-Kaldur put his water bearers where Black Manta could easily see them -- he essentially SHOWED them to Black Manta by putting them on his right side instead of inside the uniform or even on his left or turning away. It was Clone-Kaldur who shot at Black Manta seven times and missed him, putting on a good show and helped Black Manta execute (and these are Black Manta's words) "Plan B". The final conclusion of the Light? Everything is going according to plan. Then with his mission accomplished, Clone-Kaldur comes back to the cave with all his issues resolved.