I had a great answer for this before, but I can't find it. So essentially I'll summarize it as thus:

We did get to an almost universal prohibition upheld several times (by 850AD, lay usurers were excommunicated by Synod of Pavia; by the 11th Century, you had theologians holding that usury is bad again, etc.)

But there are a couple things to note.

• Not all lending was considered usurious (c.f. St. Bernardine, etc.). In particular, banking and finance actually went through the trouble of directly looking like they were usurious or charging interest.

• Pawnshops, which have been with all human cultures since the beginning of time (an exaggeration, but you get the point), were tolerated as necessary evils in medieval Europe. Different groups like the Lombards or Jews would set up shop, to which the state would sometimes set up public pawnshops in order to create market competition to lower rates.

Combine these two, and essentially people invented more and more ways to toe the usurious line so as to share in financial profit / repay debt owed but at the same time be specifically sure that they weren't guilty of usury. That being said, it wasn't until the Reformation and the Protestant churches (as well as certain leaders, like Calvin) arguing that lower rates of interest do not constitute usury that you see interest finally being cleared of its sinful status. In fact, for most Catholic countries, that declaration wasn't even officially made until the 18th century.

Interest Rates and the Law: A History of Usury; Ackerman, James M.

A history of Interest Rates, 4th Ed., S. Homer and R. Sylla