Many ideas, theories, were shared on the flight regarding the re-route to San Juan.
Most passengers settled on this one. Delta makes $$$$ on the long flights hauling cargo shipments.
Flight 479 is loaded in Monrovia or Ghana with more cargo than usual and it cannot make the longer flight distance to New York due to fuel burn rate when plane is heavier.
Delta does what makes business sense, keep the cargo load on the plane, reroutes to a closer destination, gives passengers options to get off, and call it a day.
For Delta the cost of the good will gesture in miles credited to passengers is certainly minimal compared to loss of revenue in rerouting or offloading the cargo.
If I get any updates, I will post for the record.