Why didn't he have a residence in Speyer?
The cathedral and bishop's palace in Speyer were destroyed in 1689 during the Nine Years' War. What's more, Speyer was a free Protestant Imperial City, and its relationship with the prince-bishops was poor. Schönborn's predecessors lived in Udenheim, now called Phillipsburg, or in Mainz and Trier, where they also sometimes ruled. Indeed, Schönborn wanted to rebuild the palace in Speyer, but "the quarrelsome people of Speyer" were opposed. Bruchsal thus became the new residential city.