From WebMD:Treatment for meniscal tears depends on the size and location of the tear. Other factors which influence treatment include age, activity level and related injuries. The outer portion of the meniscus, often referred to as the “red zone,” has a good
blood supply and can sometimes heal on its own if the tear is small. In contrast, the inner two thirds of the meniscus, known as the “white zone,” does not have a good
blood supply. Tears in this region will not heal on their own as this area lacks blood vessels to bring in healing
nutrients.
From me: From the WebMD description it sounds as if Mamadou tore the meniscus in the "white zone", thus requiring full surgical repair and its resultant longer recovery time. And, if I recall correctly, this is the more permanent and best long term solution for younger people, especially athletes in high impact sports, because it can restore the complete meniscus rather than just simply removing the torn piece.
There is a shorter recovery time for lesser tears where they just remove the torn piece.
UConn is apparently doing what's best for the athlete in the long term, including his life after his playing career, and not worrying about how the team will be affected this year.