I mean, did it preserve its language? Considering the state of modern Turkish - and considering how Turkish itself was not frequently employed by the Ottoman state - I'm not sure that we can say that. Look at the difference between modern Turkish and the various Turkoman languages. Ostensibly, they all developed from a more or less common Old Turkish source, but they've become different, sometimes not even mutually intelligible languages, and surely that's down to the places that each of those languages developed in and the other languages in common use in those areas.I didn't mean to suggest that all Turkic peoples are inherently resistant to assimilation. I really just meant to focus on the Rum Turks, the Ottomans, and other Turks in Anatolia. I'm aware that the vast majority of other originally nomadic steppe peoples assimilated (with the possible exception of the Magyars, who still have their language and a distinct culture and have assimilated other groups in the past. Compare with, say, the Cumans, a Turkic people who were totally assimilated). But I'm just curious why the Anatolian Turks of all these peoples successfully transformed into a sedentary group that preserved its language, adapted its culture, and assimilated other groups when the historical trend is for these kinds of nomads to settle down and become the assimilated.
And does anyone know anything about the Catalan Company?
Same with cultural adaptation, to an extent. Can you really tell whether some cultural Thing (ignoring the problems with defining salient, unique, and generalizable cultural characteristics) came about because of X "external"/"foreign"/whatever pressure or because of Y "internal"/"domestic"/whatever development, or some combination of multiple factors, or something? I mean, anthropologists have been at this for ages and there are still a lot of extremely unsatisfactory answers for these questions. That's the strength and weakness of cultural studies over the last thirty-odd years: the recognition that this sort of thing is even less cut and dried than most history (and most history is very much not cut and dried), which is both absolutely correct and infuriatingly vague because it gets in the way of making definite conclusions.
In any event, the line between assimilator culture and assimilatee culture isn't exactly as well defined as I think that you think it is.
If you're looking for a reason for what you refer to as the success of the Anatolian Turks, perhaps it's as simple as political contingency. On the face of it, the creation of the Selçuk empire was a wildly improbable event. Its fragmentation into successor states that mostly managed to retain their independence was also improbable. If either one of those things failed to happen, the entire notion of Turkish Anatolia would be utterly stillborn. Searching for big, overarching, sweeping macrohistorical forces behind these events seems silly to me when none of it might have happened had some military-political coinflips turned up heads instead of tails.