'69 Grand Torino - Drum came off

I actually have a 1969 Gran Touring Torino with 350. I replaced the drums and rear brakes 2 days ago. I made a left turn this morning and my drivers side rear tire and drum came off. Needless to say, I’m unhappy. Dented my uni-body quarter panel and who knows what else to my suspension.
Any ideas why this would have happened? Did they sell me the wrong drums? I know I tightened the lug nuts.

If all that came off was the drum and tire, you didn’t PROPERLY tighten the lug nuts.

I was afraid of that