I have seen a couple of different sources but most seem to site between only 100 and 300 knights out of the estimated 5000+ who participated in the 1st crusade on the side of the Christians choosing to stay in the Holy Land. Why was this? Was it concerns over politics back at home, was the wealth/trade potential of the "Holy Lands" such that it could only sustain such a number, or was this some grand conspiracy to consolidate power for Baldwin the 1st?
In fairness, some if not many of the original estimated 5000 were killed, however exact numbers appear to be unavailable. Even if only 2500 remained, 12% choosing to stay seems very low. I would love some input from historical sources, especially those which are more obscure.
Contrary to some threads of popular history, we have no real evidence that the First Crusade was "colonialist" in its intent. That is, we have no real reason to believe any of the crusaders set off with the intention of remaining, the idea that the Crusade was mostly second sons seeking wealth having long ago been put to rest. Indeed, even the motives of Urban II in calling the Crusade are obscure, clouded by the lack of reliable and mutually compatible reports on his sermon at Clermont. And historians have even pointed to the information you reference as evidence in support of the idea that the Crusade was really a sort of "armed pilgrimage" with no overarching designs of conquest.
Actually, the inverse of your question is, in some ways, even more curious: if we accept the idea that the Crusade was generally seen by its participants as a pilgrimage, why did any of them decide to stay at all? After all, after a successful pilgrimage, one returned home. Was the decision to remain purely a conquering reflex, a pious impulse, or something else? Here, too, source problems defy our attempts to pin down solid answers. But it's also true that the reasons certain people chose to remain were highly personal, and that any attempt to generate an overarching answer is doomed to be labeled reductionist.
I would certainly read Jonathan Riley-Smith's The Crusades: a History (preference for the 2nd ed.) if you have not already.
follow on question to provide more depth, perhaps you have the context:
Does the presence of knights only indicate "Generals" and what is indicated for the amount of total manpower implied by that number?
Is there any context for how the remaining knights were distributed or allocated within the crusader states?