2003? KIA SORENTO. RUNS, CRANK PULLEY DOESN’T SPIN

I was out at my friends place having a couple drinks. My other friend decided to come over and have a couple drinks as well. At one point he wanted to show me his subs in his KIA. When he started his vehicle up I heard this rattling noise coming from the engine compartment. He said he lost his power steering, his brake light came on… etc. He told me it was because he had bare wires for his CD player and he thought that because he was screwing around with the wires he lost his power steering. I told him no that cant be so I got him to pop the hood. The motor was running, cranking obviously but the serpintine belt wasnt moving. I felt his belt it was tight and everything seemed okay on the outside. I told him he is lucky that his water pump was connected to his timing chain and not the serpentine belt otherwise he would have overheated and caused more problems. I am suprised his battery didnt die for the distance he went to get there with no altanator. Now it also sounds like something is rattling around inside the engine. What could have caused this issue. It’s just weird. Could it be something to do with the crank pulley or could this problem be internal??