> That's not an "existential threat". No European state bothered to care about that piracy until Sweden and the US in https://en.m.wikipedia.org/wiki/Barbary_Wars . The bigger states were evidently happy to pay the tribute—this is cost cutting not defense.

That strikes me as a West European-centric view, "the big West European nations weren't threatened and nobody else matters". From https://en.m.wikipedia.org/wiki/Slavery_in_the_Ottoman_Empir...

> Sixteenth- and 17th-century customs statistics suggest that Istanbul's additional slave import from the Black Sea may have totaled around 2.5 million from 1453 to 1700.[4]

Also

> In the devşirme, which connotes "draft", "blood tax" or "child collection", young Christian boys from the Balkans and Anatolia were taken from their homes and families, converted to Islam, and enlisted ...