They don't call it electro-magnetism for nothing, but in your case it's coincidence.

Changing magnetic fields induce current in conductors, static fields do not.

Unless you have a way to move the magnets and the wire is in their field it is coincidence.

Most likely caused by moving the fixture to attach the crystals.

Probably not entirely a coincidence. The odds are that the lamps may have been in there a while, add in some jostling and shaking of the fixture while the crystals were installed. Lamp filaments are fragile. It doesn't surprise me that a couple lamps burned out actually.