Was that the first or second league war. Winning the first one (the Schmalkaldic War; which only allows electors and the emperor to get involved) just makes the emperor tolerate Lutherans while not making protestantism dominant generally or winning any acceptence for more radical reformers. Winning the second war (Thirty-Years War) where everyone can get involved is the only way to make any protestant faith the dominant religion.

There was a "first conflict" which I was not a part of (and I am unsure as such, if it ever was triggered), but this was the second religious conflict where everyone could join.