Merry de Val took on the name Alexander VII, in honor of the last Spanish pope, and his selection was met with muted and reserved approval throughout most of Catholic Europe, with him regarded as a brilliant intellectual but his conservatism suggesting more of the same from Serafini. For his own part, Ferdinand II of Austria-Hungary saw his effort to anoint a name other than de Val backfire - Italy still was hostile to the new Pope, and he had earned powerful enemies in France and the Roman Curia whom he now needed to appease, arguably with a more aggressive stance geopolitically against "heathen" Italy and Protestant-dominated Germany..."
- God's Kingdom: The Catholic Church and the 20th Century
(As I've mentioned before, the Church stays much more conservative, and for longer, ITTL, but de Lai was a bridge too far. Merry de Val is one of those cliche alt-Pope choices, but he is one for a reason, so he'll make a perfectly fine Alexander VII for my purposes.)
Small quibble - I think his name would actually be Alexander IX. The last Alexander before this was Alexander VIII who died in 1691.