I was on a team with two Kenyans (one a multiple time NCAA champion in cross country and track) and another (my roommate) who competed only as a freshman (top finish in NCAA 3rd) and then went professional. We also had another Kenyan (former NCAA champion) in town who was past his eligibility but still finishing his schooling.
In order for this pipeline of successful athletes to work, the coach had deep contacts in Kenya and was able to vet the athletes before bringing them in. I was only on that team for one year, but it seemed to me that a big part of the lead generation for recruiting sort of went through the current athletes. In other words, the coach would ask his current Kenyan stars about people he was recruiting to find out if they were legit and also find leads for people to recruit through the athletes' contacts.
I didn't know the details of these guys' scholarships, but I'm pretty certain they were both on full rides. Certainly my roommate was, as he had no money to his name and was not working a job, so no way he could come up with extra money for school expenses. There are challenges to surviving in the USA with zero support, and living with this guy made me sympathetic to what athletes who come from poverty go through. For instance, coming from Kenya, my roommate was completely unequipped for dealing with a harsh winter. I don't know how much, but I know the coach was giving my roommate some cash under the table for survival expenses. When Christmas came around, my roommate traveled home with me and I told my mom not to buy me anything and we went out and got my roommate a solid jacket, quality boots, and a bunch of winter clothes. Others on the team pitched in from time to time to help out since we were all close friends. I didn't really keep track but I probably paid for the majority of our food since I wasn't really hurting for money.
Regarding their educational achievement, I didn't have direct experience with our other Kenyan teammate, but he graduated with a degree in engineering and was an excellent student. My roommate spoke very good English (Kenya is a former English colony so most of them speak English). His written English was not fantastic, but not a disaster. I edited his papers and it was a lot of minor stuff, so he was probably better than the average American student. He worked very hard at school, and though initially graduating with a kind of general business degree, went back at school hard and worked his way from a bachelors through a PhD in a scientific subject, and is now a professor. He became a US citizen through WCAP, is a very intelligent and wonderful person. Probably the highest quality human being I've ever known in my life.
My roommate went professional after his freshman year because of financial reasons. I don't know if I had the story exact but I believe he wanted to work a job in the summer so he could earn money to send home to his family. The incoming coach would not sign the required paperwork allowing him to work a full time job (some kind of NCAA regulation which I didn't understand) so he gave up his scholarship and went pro on the roads, earning something like $80k that summer (it was a long time ago so that was a lot of money). He eventually ran very well at distances from 10k to marathon.
Overall, for our team, Kenyans won a lot of individual NCAA championships for us, so they tended to pay out. This was probably entirely due to the quality of the recruiting pipeline. Most of them stayed the full 4 years. Without the pipeline, I can imagine it is difficult to get something like this off the ground without a lot of mistakes being made. Most coaches probably weigh the risk/reward and don't think it's worth it. Now that US kids are running so fast, it's probably a better bet to build out your team with second tier guys on partials. If you're going overseas, it's probably a lot simpler to recruit Europeans and Australians who have more easily vetted credentials.