The day of MU earnings I sold 4/17 $450 puts for $39. Over the next five days, MU traded down to $320 or so...and the put to $150. I thought for sure I would get early assignment. Never did. Now MU back to $420 and the put is $34. I certainly would have closed or exercised if I was the put buyer. What am I missing? Please explain the different reasonings for not closing/exercising.