I was reading up on the satellite hacking communities back in the 00’s. 1969, that old stuff had only basic security if any at all. It’s possible that anyone all the way down to an amateur might have commanded it to move.

From the description it sounds like it’s orbit has become somewhat elliptical. If some state entity was trying to screw with it, they probably would have left it in more of a stable geosynchronous position. You don’t have to move it far to make a point.

Seeing that it’s dead and they’re not likely to have logs from it, maybe it had a malfunction or a propellant leak.