There is a lot of misunderstanding here about the history of AoD building. Look back at the mid-1800's and beyond. The Catholics here know that Sunday Mass is an obligation. There was a greater sense of obligation in earlier years and no one would miss Mass. But there were no automobiles and such transportation was even't conceivable then. Most Detroiters [[most City people) didn't keep horses and carriages. They just walked. So, the AoD had a policy of common to most American urban diocese' to purchase land every square mile for the eventual building of a parish church [[the closer proximity of the three Polish churches on Canfield was an aberation that caused a lot of trouble when the third one was built without the Bishop's consent) . Every Catholic had to be able to easily walk to church. In some ways, a version of that policy continues today. The AoD was still purchasing land for eventual parishes within the boundaries of the diocese until very recently.

But, just so you know, the AoD usually did not "build" the church buildings. Once the population of a neighborhood was established, a new parish would be established, named and a pastor assigned. That pastor would start having Masses in a rentable building in the neighborhood while rallying the parishioners to raise the funds to choose a design, an architect and the amenities of a church building, a school [[in earlier years), etc. For example, the first Masses at Holy Redeemer Parish in Detroit were said in a space above a tavern on West Jefferson circa 1880. The parishioners eventually built three successive churches, schools, convents, an theatre on West Vernor, etc. The Diocese did not construct these buildings that were the ambitions of the parishioners.
Many parishes had much more modest ambitions. But, in general, the pastors assigned to build Detroit parishes were ambitious builders, building for the ages. The AoD is a corporation sole, so the properties do belong to the Bishop - but the parishioners built their parishes - and continue to build them where they live.