>>23446987
Thunderbolt's Von Braun is less of a "city" proper and more of a giant Anaheim facility. The actual civilian population is small, since most of the space in the domes is used for the terrariums and Anaheim's manufacturing facilities. Destroying it is the same as, say, Allied bombers destroying the Ruhr industrial facilities during WWII.
There would be collateral damage, obviously, but it's a far cry from a vengeful act of civilian extermination.

It's clear that Levan Fu saw the future and had a glimpse of Anaheim's weapons as the spearhead for all the conflicts across the Earth Sphere, from the OYW to the Zanscare War. Everyone was using MS that were built and/or designed by Anaheim. While destroying it wouldn't do much for the ideological/political side of things, it would certainly cripple everyone's ability to wage war.