Barbatos was very weak.
He was truly far too weak.
Once upon a time, he had been the strongest creature on the current timeline of the entire Multiverse. Back then, he still had no idea about the hidden problems his master, World Forger, had left inside him.
Even when Supreme Superboy and Parallax Hal joined forces to invade his World Forge, he had been able to drive them away by himself. He had used a few tricks, but he had indeed done it.
But times had changed, and all of that had departed like a dream. Fighting Perpetua and Empty Hand had consumed too much of Barbatos's power, leaving him so weakened that he might now be countered by his own Servitor God, Batman Dragon.
As long as he was given time to recover, Barbatos might still have been able to reclaim his former strength--
Barbatos had once been powerful. Just as Anti-Monitor intended to alter history and bring the fact that [Anti-Monitor was powerful] back into the downstream of the Over-Time Stream, Barbatos could also find a way to overwrite his powerful past self onto his current self.
That was the most classic method of the DC Multiverse. On the grand Over-Time Stream, before space-time and history had solidified, anything could be altered at will...
The so-called [facts] were never unchanging things.
So now you understood why, after Mother of the Multiverse Perpetua came down from the Source Wall during the Death Metal period, the first thing she did was smash the Over-Time Stream.
She had finally gotten down with great difficulty, only for history to be altered the moment she turned around, binding her back onto the wall. How could she allow that?
Boom! The Over-Time Stream was done for.
Moreover, as far as the current Barbatos was