Who did the admin design for wordpress?

Does anyone know the main designers for wordpress?

Nope.
Probably one of the developers.

There is no accounting for taste. ??

so nobody knows the person who designed the admin section??

It’s been a long time. And anyway, it probably wasn’t one person, WordPress is a collaborative effort.

You could go look through Trac for the code history, but I doubt it goes that far back.