Alternator Problem

I have a 2001 BMW 740i w/ 100,080 miles. I recently had the intake manifold gaskets changed for an oil leak as well as the water pump replaced for a leak. After having that fixed I was driving home a couple of days later and my alternator siezed up. This caused additonal problems. My question is whether this is just bad luck or if it is possible that while replacing the water pump and the intake gaskets if they could have messed up the belt on the alternator causing a chain reaction. I appreciate any helpful answers. Thank you.