The Franciscans were booming, with their charismatic and already sainted founder and a radical evangelical way of life, so that attraction is obvious enough. The Dominicans, too, though Dominic himself seems to have been less of a draw card than -- what? their well-organised way of life, the allure of education, nothing succeeding like success, the attraction of the preaching ideal? The attractiveness of these orders is attested not only by their rapid expansion but also by donations and the rush of guilds and so on to associate themselves with their churches, but this does not happen with the Carmelites (and Augustinians) until after 1350 when they finally start attracting more money and patronage than the larger orders (Hervé Martin's book Les ordres mendiants en Bretagne (vers 1230-vers 1530) (1975) is very interesting here.

But the 13th-century Carmelites, for example? How did they attract sufficient candidates to keep expanding internationally at a fairly rapid pace? The young order, like the Augustinian Friars, must have been racked by tensions as it transitioned from a rural eremitical life to an urban mendicant one, their dress was outlandish (they had to petition the pope to change it in 1287), their future was uncertain, there were no big names, they offered few educational opportunities for ambitious young men (they did not enter the universities until the end of the century). One has to wonder how much preaching they actually did, given their lack of qualification and the almost total lack of evidence they have left behind (there are next to no preaching manuscripts by Carmelites even from the 14th century, and virtually no writings at all from the 13th). Their friaries were nearly all on the wrong side of the tracks. It's unclear whether their substitution of their traditions about Elijah and Mary in place of the usual narrative of a charismatic founder would have functioned as a benefit or a liability.