Were all 'sundered' versions of original amorotians. The echo is implied to be a fragment of the power amarotians had, and is not gifted by Hydaelin but inherent to all of us because of us being sundered versions of those amarotians. The star shower or events that mimic it awaken that power. IIRC Elidibus does explain that you cant hear haidelyin without the echo, contrary to the original belief you hear Hydaelin and then she gives you the echo. You dont believe me, fine, Ill quote the wiki:

Originally Posted by
https://finalfantasy.fandom.com/wiki/Elidibus_(Final_Fantasy_XIV)
...Elidibus later makes his presence known at the Crystarium, casting an illusion of a starshower to awaken the Echo within those present
This was revealed in the most recent MSQ. How can hydaelin be gifting us with the echo if it requires an external event to awaken that power? In this case,
Elidibus awakens the echo in the crowd by casting an illusion. Wouldnt it be counter productive to Elidibus to even create more WoLs with the power bestowed by Hydaelin if thats where it came from? All these people would be potential threats to him. Yet hes trying to make more people with the Echo.
If I had to take a guess, he wants them to all go out in the world, do what the WoD did inadvertently 100 years prior, and jump start the flood again.