Script is not broken.
I tested it myself now and they dont spawn all at once but in a very very short interval:
2020-07-16_23-56-15.png
Seems like misconfiguration of the system.
Whoever made the quest also didnt add an a waypoint for the mobs to actually invade, so they just.... Stand there :)
Going to leave it to the author of this invasion/love story to handle as they know best what they intended to do here.
