It wasn't meant to "control" as in an evil way if that is what you mean (not sure if you did). It was a good system for the time since lots of horrible things have happened. The bible is a beautiful book with deep universal truths. People needed it. People that follow many of the universal teachings are having amazing life since they have great guidelines to live by. It's amazing and timeless.
Even the bible states that the kingdom is within. They are talking about heaven so all people could understand it in a beautiful way. Fear is a thing that they have seen that if people learn to be fearful of certain things then they will behave in amazing ways. They all point to the same universal truths but just in different ways.
The Bible does contain many truths, but during the Middle Ages, to which @lynncoyle1 spoke to, it wasn't readily available to the people. That didn't start to happen until the period of the Reformation, which came after. So, the Church did have primary control over the interpretation of the Bible and, at least according to the reformers, not all of what they taught was biblically based.
So, I would say you could debate either side of the control issue, whether it was actually good or not and probably have a fairly long list on both sides. I believe some pretty good people went to their deaths as heretics because they dared to interpret the teachings in the Bible differently than the prevailing doctrine of the Church.
And the fact that the peasants in the Middle Ages had no idea how to read, and that bibles weren't printed en mass yet, it was pretty easy to alter the writings. Your point about heretics is also a poignant one.
As always @glenalbrethsen, I appreciate your input.
I should have clarified, but no I didn't mean "evil" per-say , but I guess people can view the intentions behind the word 'control' how they see fit. I also didn't say anything about the bible, because the bible, and the church's use of control in the Middle Ages are two completely different entities. I respect your beliefs and appreciate your comment though.