Just to break the numbers down so it's easier to see why so much damage occurred. Lets say you stood on it for 10 seconds. You say you drove it 90 miles "here and there", so i'm going to assume that you got on it at least once for a short bit. Let's pick 10 seconds of time, with full throttle and full load on the motor. For the sake or simplifying the math, we'll say you hit 6000rpm for those 10 seconds. You basically shifted from 1st to 2nd to 3rd and held third for a bit.
6000rpm= 100 revolutions per second
100 revolutions in one second= 50 firing sequences in one second
10 seconds of run time = 500 firing sequences on each piston
With a heavily advanced timing adjustment and/or poor tune and/or poor gasoline, you had yourself "marbles in a coffee can" type of detonation. Imagine the beating each one of those pistons took getting hit with 500 secondary flame fronts as they collided with the primary flame front. A hypereutectic piston simply cannot handle that type of abuse.