(1) Why aren’t Haitians in the Dominican Republic much interested in baseball, in that otherwise baseball-crazy country? Probably for much the same reason why Haitians in Haiti aren’t much interested in baseball. This article could have ended at the start of the third paragraph.
The same people just moving to the other side of the island isn’t going to change them all of a sudden. The DR doesn’t have magic infield dirt.
(2) Lots of theories, but I think there’s one very simple and obvious one they’re missing, maybe because they want to miss it for the purposes of the politics of racial agitation (this is The Undefeated, after all)
The law of diminishing marginal returns.
There are fewer and fewer “first gen” D-I scholarship college athletes, men’s basketball and otherwise, for the same reason you hardly ever hear “I’m the first in my family ever to go to college” anymore. That’s because, cue Pepe, it’s the current year, not 1939. We are now so many years into the societal expectation of near-universal tertiary education (for all but the most obvious dullards) that we’re at least two generations in that era, three depending on the demographic. So of course it would be the case that it would be hard to find a college student these days, scholarship athlete or not, who didn’t have at least one parent who went to college.