ORAC
At around 1:36:30 on this video you see a massive explosion well after the booster touched complete with mushroom cloud.
The point is that the booster has substantial stored explosive potential which can level a large area if they don”t catch the booster perfectly and there are no post landing fires.
The upper stage was always suppose to survive and land.
While they did accomplish significant technical achievements, they are still batting 0 on reusability.