Peace, one and all...
I had an interesting conversation today about the Baha'i faith. As it happens, or rather as God willed it, the Baha'i faith is an area I'm interested in (as an outgrowth of Twelver Shiism). As we were talking, it occured to me that the 19th century saw the emergence of quite a few Islamic messianic religious movements. For a start, the Bab and Baha'ullah both emerge in mid-19th century Persia (during the Qajar period). In contemporary India, Mirza Ghulam Ahmad began preaching the message of Ahmadiyya. Then, over in Sudan, Muhammad ibn Abdullah al-Mahdi was also a prominent force at this time. Although not exactly in the same category, one might even include the Sanusi movement of Libya.
Why should the 19th century have witnessed so many messianic movements? Well, quite apart from purely religious answers (which lie within the realm of faith), perhaps the impact of colonialism can also offer some insights. That is, looking at the above list, every messianic movement began in a land colonised by a European power or else heavily influenced by it (as with Persia). Perhaps these movements can be seen as related to wider Islamic reform movements of the time: Muhammad ibn Abd al-Wahab in what was to become Saudi Arabia; Muhammad al-Shawkani in Zaydite Yemen; the Deobandi movement in India; the Shaykhi movement within Twelver Shiism. Interestingly, only two emerge from a broadly Shii milieu; the other examples cited here all arose with Sunni Islam.
The list can be lengthened, but I think the general point is clear. If nothing else, there is room for an interesting research topic here insha Allah.