I will comment from the perspective of someone who went to new worlds on EU.

1) establishing a new world or DC requires forming bonds, FCs, new statics even. This takes alot longer than 1 month to achieve and those who have transferred will likely be putting all their time into that right now. Running 'easy' content for loot to rank up the GC and then FC for example.

2) other games including online games such as wow and genshin are putting out bigger content right now. Yoshida did say FFXIV will experience a slowdown on content and patches but i dont think anyone was quite prepared for how bare-skeleton the patches were about to become. This has pushed players towards the other games too. This affects all DCs but particularly the new ones because of the time investment required.

3) housing wasnt enough of a reason to move to a new world or dc. The "crisis" was such because of a few loud players hyping and ranting rather than thousands in actual need. On my homeworld Sagittarius for example there are still roughly 400 empty plots.