The Ottoman conquest of the Mamluk Empire looks like an impressive act at first glance, tripling the size of the Ottoman domain, opening the gates to North Africa, and securing the title of Caliph for the Selim Yavuz and his heirs.
If you think about it a bit, it can be argued that it did more harm than good.
The ability of the government in Istanbul to actually _control_ Egypt and the Levant (let along the Maghreb) was spotty at best (the Malmuks effectively controlled Egypt until the 1800s) and the centrally controlled army often found itself overextended. Meanwhile the increased influence of the Uelma on a government that found itself in many ways the guardian of Sunni Islam Orthodoxy was under more and more pressure to dismiss otherwise good ideas that were excessively heterodox and/or heretical.
Since it is unlikely the Malmuks could have _won_ a war with the Ottomans by the 1500s, let us say that it falls apart a bit earlier whilst both Istanbul and the Savafids are distracted. There are some land grabs (Antioch and SW Anatolia on the Ottoman part for certain), but the rivalry between
Selim and
Ismail start playing itself out via proxies.
In short, instead of becoming the overlord of the Islamic World the Ottoman Empire remains a half-Christian European marcher state.
Now what?