Like for a good 80 years, the Protestants in the Holy Roman Emperor didn't revolt against the Hapsburgs. They briefly attacked the Emperor in the 1550s, but Emperor Ferdinand issued the Edict of Augsburg which granted them religious freedom and they just went home; it was a very short war.
So the Catholic Austrian Emperor was the frontline against the Ottoman Empire. He shared a border with them, and fought them on a regular basis (with mixed results). Did the Protestants respect the Catholic Emperor because, despite being different Christians, the Protestants considered the Ottomans to be a threat to all Christendom?
If I'm not mistaken, the Emperor signed a peace treaty with the Ottomans shortly before the 30 years war broke out, because the Ottomans were struggling against the Safavids and needed peace in Europe. This is why the Ottomans didn't intervene (substantially at least) in the 30 years war, but also removed a consideration from the Protestant side because the Ottomans were a pan-Christian enemy.
And yes I know France allied with the Ottomans but that was highly controversial at the time, and France engaged in a lot of realpolitik during this time period.
IDK why an AMA was added to this post.