The belt could have broken for 2 reasons...
1. It was worn out (old)
2. Something is binding the center (transmission pulley)
Your husband can remove the belt and try turning the center pulley by hand to seee if it is bound up. If so, the bearing is a possiblility, as well as something caught between the spin basket and the outer tub.
Other than that, it is easy to get the belt on wrong when replacing it for the first time...we all have done it. If you get grease on that belt, you will ruin it. Amana belts are specifically designed to sl;ip a bit during the spin cyle.