What prompted the change in Christian attitude towards usury?

Question

Lending with interest between Jews is a sin in the Old Testament, which should have gone away for non-Jewish Christians

According to Wikipedia, it was only proscribed by Christianity later; at first only applying to priests.

The First Council of Nicaea, in 325, forbade clergy from engaging in usury[13] (canon 17). At the time, usury was interest of any kind, and the canon forbade the clergy to lend money at interest rates even as low as 1 percent per year. Later ecumenical councils applied this regulation to the laity.[13][14]

Later on, usury became even more emphatically proscribed.

Lateran III decreed that persons who accepted interest on loans could receive neither the sacraments nor Christian burial.[15] Pope Clement V made the belief in the right to usury a heresy in 1311, and abolished all secular legislation which allowed it.[16] Pope Sixtus V condemned the practice of charging interest as "detestable to God and man, damned by the sacred canons and contrary to Christian charity."[16]

Theological historian John Noonan argues that "the doctrine [of usury] was enunciated by popes, expressed by three ecumenical councils, proclaimed by bishops, and taught unanimously by theologians."[14]

At what point did the official Catholic position on moneylending change and why? If the change happened after the Reformation, did Protestants have a separate reason?

Answer 1

Evidently it was John Calvin who began the process of changing minds about usury by redefining it from usury to interest and outlining its importance. Here is a link to his letter.

Chapter XI - Calvin's letter on usury

As to Catholicism, Schaff (who also references Calvin) says this about its change of policy re Canon 17 of Nicea Council forbidding usury.

"Among Roman Catholics the new doctrine began to be defended about the beginning of the eighteenth century, the work of Scipio Maffei, Dell’ impiego dell danaro, written on the laxer side, having attracted a widespread attention. The Ballerini affirm that the learned pope Benedict XIV. allowed books defending the new morals to be dedicated to him, and in 1830 the Congregation of the Holy Office with the approval of the reigning Pontiff, Pius VIII., decided that those who considered the taking of interest allowed by the state law justifiable, were “not to be disturbed.” - Excursus on Usury

So, the change was prompted by understanding that money produces money, just as a farm produces crops (money). If the latter is okay, why not the former? Calvin: "“And what else is it than to treat God like a child, when we judge of objects by mere words and not from their nature, as if virtue can be distinguished from vice by a form of words."

Answer 2

There's an article here that argues (convincingly, in my opinion) that it has not changed.

Even if you end up disagreeing with the conclusion, it's extremely informative, and has a wealth of source material.