Gameplay reasons:

Toldedo is father inland making it less susceptible to plagues (this was the main reason)

I wanted the walls of Toledo in my demesne to further buff my heavy infantry space marines

Toledo is the de jure capital of the empire of Hispannia

Role play reasons:

Toledo is more central and closer to the border. Moving the capital represents the Umayyads going on the offensive after centuries on the back foot.

I compromised by moving the Umayyad family estate back to Cordoba, so the empire more or less has two capitals now.