One way to control people is to keep them illiterate. If they can't read or write, people are less likely to disagree with civil and ecclesiastical laws that are imposed on them. Or, if people can read and write their own language ("the vernacular"), the best way to control the flow of ideas is to write all scholarly, legal and theological works in a foreign language (like Latin, for example.)
In 500 AD there were about 400 vernacular translations of the Bible. Not long after, there was only one legal translation: the Latin Bible of the Catholic Church (the "Vulgate").
By the time John Wycliffe was a scholar at Oxford in 1360, the Vulgate was still the only legal Bible people could use. And, since common folks couldn't read Latin, and only priests could have a direct relationship with God, people had to accept what their priests told them. There was no method by which individuals could study the Bible and then disagree with the Church's interpretations. If monks and scholars couldn't disagree, how could the average man?
John Wycliffe was fed up with that state of affairs. Between 1360 and 1382 (or thereabouts), he and his Oxford associates translated the Bible into English. Wycliffe did not use Hebrew and Greek original sources. He used the Church's Latin version, and translated that.
At first English officials supported Wycliffe. They loved his beliefs that England should not have to pay huge amounts of money to the Catholic Church. But as Wycliffe became more radical in his thinking, the secular authorities distanced themselves even as the common man supported Wycliffe. He had given them something they never had before: A Bible in their own language.
As the Church's authority began to tighten around Wycliffe, he was expelled from Oxford in 1382. A series of strokes prevented further action against him at the time, and he died on December 31, 1384. The Church wasn't finished with John Wycliffe, though. His books were banned, but not before they were smuggled out of the country to Prague, among other places. There, they came into the hands of John Hus.