Secular leaders had little to do with the rise and strength of Protestantism.
The real strength of Protestantism came from the vast and real revivals that came during that time period where thousands upon thousands repented and were born again as new creatures in Christ.
God may have used these two leaders in some sort of tangential way, but it was the Holy Spirit led revivals that changed the world during this time-frame.
“Secular leaders had little to do with the rise and strength of Protestantism.”
- Not with the rise and basic strength of Protestantism itself perhaps.
But, never forget the St. Bartholomew’s Day massacre (Massacre de la Saint-Barthélemy).
If Sweden wouldn’t have intervened and wouldn’t have laid siege to Germany for 15 years, this part of Europe would definitely have been Catholic today, the Nordic countries probably would’ve been too and perhaps even Britain and the US!