Unlike the Argentinian Bishops, Pope did not want to oppose gay marriage.

There is objective data. For instance, at the beginning of the debate about the gay marriage bill in his country, Bergoglio suggested that all bishops should opt for a moderate approach, such as leaving open the intermediate consideration of de facto unions. His political perception was there: he knew that former President Néstor Kirchner was going place high stakes on the matter, exerting pressure on legislators with both good and evil arts. Besides this, the Cardinal believed that the unfortunate manner in which the Episcopate had opposed the divorce law in Argentina could not be afforded. He thought, eventually, that across the board opposition was counterproductive. In fact, that was the single occasion when, as President of the Episcopate, he had lost a vote. Future events proved he was right.

Souce - have improved their English a bit