It was a shame.
Yes, it was an event where the Judgement Order was supposed to practically collapse, leaving no more than four members alive, and yes, Alexander's interference made sure a majority of them lived.
However, he couldn't save everyone.
The laws of causality didn't allow him to create a "perfect" timeline, because such a timeline would be nothing more than a dull existence without any semblance of reality.
Therefore, Alexander couldn't intervene as he pleased.
He had to wait for that signal.
That moment when Rose activated the array and summoned a helper.
The person who was originally meant to take that place wasn't reliable in the slightest. He was a member of the Angel Race named Deraphiel, someone who didn't have much presence in the universe.