One of the significant problems with understanding Islam has to do with entire debate of what is Islam.
Okay, so one wants to understand these Muslims. Which form of Islam should one study? Sunni Islam? Then what about Shiite Islam (which is quite different from Sunni Islam)? What about the different schools of jurisprudence within Sunni Islam? What about the various movements therein: the modernist movement, the Salafi movement (which includes the Wahhabi and Deobandi groups), the Ahmadi movements (whom most Muslims declare to be non-Muslim), the various militant movements? What about local forms of Islam that mix elements of the old religion with Islam? What about Sufis, both the ones popular in the West (considered heterodox and heteroprax by most Muslims) and those popular amongst Muslims (but would seem to Westerners to be intolerant and too inflexible)?
And then obviously issues of major concern would be related to law, the form of states, and jihad. Each has a plethora of theories, practices, movements, ideologies, paradigms, groups, propaganda, and interpretations.
See, part of this has to do with the Salafis’ efforts to establish the narrative that there is one Islam (which happens to be their type). Other groups do not challenge this because doing so would reveal to the world that Islam is fractured, which would desecrate Islam and its image before the infidels. Plus, some agree with the Salafis and are ashamed of their internal divisions. (Or they agree with the Salafis because the Salafis expertly justify their every belief and practice using the standard sources of Islam.)
In any case, “understanding” Islam is far more difficult than some may think.