Issues with 340 distributor

Hey guys, im a pretty acvtive preventative maintenance nut. Change fuel filters every year along with oil. Change plugs every two years. Well its been about four years since the cars been done and decided to replac the distributor cap and rotor. So got them in mail today, swapped cap over no issues there. Noticed that the rotor is a little snug on the distributor shaft. Pulled it off and put new one on. Put everything back together and no start, wtf. I knew firing order was correct because I swapped them over one by one. So i noticed that the rotor spun with a pretty good amount of play, then also noticed that it was spinning freely which i know it shouldnt. Crap. Pulled distributor and noticed the distributor shaft knurls had come loose from the upper part of the distributor. When i pulled the rotor off I remember the upper mechanism moving quite a bit. Upon further inspection looks like the advance mechanism pulled out of the distributor base. But why would it? Isnt it supposed to be fastened to the distributor base? Mine looked more like just line up pins to me. Any thoughts