Why were religion tests banned from the constitution?

The easy answer is to avoid the problems which are incumbent in a (religious establishment) in some countries, where they have an established church, it gets often far beyond the church buildings and even educational facilities- for example the Established Church in Denmark (which is evangelical Lutheran) operates a state-run Farm credit bureau, now if you need to finance a new tractor...) Nothing like this exists in the United States! The idea was to reinforce the (Wall of Separation) this does not exclude Chaplains in the senate and the Armed Forces, however.