If it was a senior JUCO player it was probably a cash-saving move. Filling the last slot with a scholarship body, even ifyou know he won't sniff the court, saves 25 percent of your leftover cash. If you're trying to rebalance classes or there's simply nobody left that you like going after, it's a quick and easy way to conserve that cash for the following season.
If it was a junior or soph JUCO, then the potentials must have been good or something, and the JUCO may have showed on the D2 list at one point when it first caught the player's attention...I don't know. That's a harder scenario to rationalize.