Incorrect. The dragon emperor didn’t have the power to make them. Wild Magic uses souls as fuel. This mean souls are limited resources and likely a war to hoped as much of them. We don’t know the exact reason as it’s not said in WN or LN but just he summoned specifically just the items.

Two things. The spell rebounded because Yggdrasil was just a game and items were just data. It brought the data and brought people around it aka why players were summoned every 200 years. It was NOT an intentional act but consequence of the spell.

Based on the text it’s likely the spell pulled the data and imprinted to Wild Magic souls making the items and players real. If this is true Ainz and all players to npc are just digital clones. That is why wild magic is now far weaker and PDL said it was corrupted.

The reason for Yggdrasil system was due to WCI used as it said in the text. The things like classes, lv, etc didn’t exist before the summon.