Protestant minority in Italy

During the protestant reformation there were at least 15,000 Italian protestants. They were viciously suppressed by the catholic church.

How can we have by the present day a minority of at least 20% protestants in Italy?
 
Have the Habsburgs turn Protestant (in a universe where they don`t inhabit Spain, for plausibility`s sake, but the Reformation still takes place as a German thing, which is tough but possible). They controlled a lot of Northern and North-Eastern Italy. If they`re not into Spain, maybe they`ll try to gobble up more Italian duchies / city states / ... in the North.
 
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