Because the guy in charge of it is capable of pattern recognition, noticed Chaldea murdered it's way through like six world ending threats, wisely decided "hey I should actually prep for them", and worked with the gods in the Lostbelt to prepare for their arrival. And by prepare i mean they immediately shot Chaldea with an orbital laser cannon as soon as they peeked their heads out and sent an entire navy to hunt down everyone who survived. So LB 5.1 is basically just Chaldea desperately trying to get its foot in the door so they can actually go after the stupid tree thing they came to kill. :skully