In a way, they're like the hobbits living in the Shire. Only there has been no Gandalf who came pounding into a friendly village and warned Frodo and his friends.
Instead, the explorers started on their journeys from all around the world, and almost all set out alone, unexpectedly, on their voyage of discovery. What's in the Qur'an? No one told them. No one warned them. And what about the other Islamic religious texts, the Sira and the Hadiths? What's the history of Islam? Is this a religion of peace? And what does peace mean in Islam?
Some had an idea from earlier encounters with Islam. Some had an idea as they were Muslim. But being Muslim didn't mean they knew much. Also, Islam doesn't encourage questioning.
What are Islamic beliefs, many of the explorers asked, one after the other? What is jihad? Why are there, throughout history, so many Islamic jihad attacks? And what about the current Muslim persecution of non-Muslims, so that over 100,000 Christians are murdered annually for being Christian by Muslims? And what about the murder of Muslims by Muslims? - currently there are about 25,000 such murders a year. And what about all those fatwas? Death threats. Murders and attempted murders.
Not all looked at the same questions. Some looked at culture, did not want to look at religion. Some did not want to look at the Qur'an, or found ways of not accepting passages calling for violence to non-Muslims, etc.
But wherever they started, for virtually all (not all) of those searching, if they went through the Qur'an, many of the findings have been the same. The Qur'an - it contains passages calling for the death of infidels and apostates. It contains a mass of Jew-hatred. In life, there is no equality between women and men - though there is after death, on judgement day (when women will be judged for their obedience to men).