My family manufactured and hired out bouncy castles for years (20+) and never did one incident like this happen. Because there are two very simple rules when it comes to wind and inflatables-if it’s over a certain wind speed the hire does not go ahead and they are always, always properly tethered. Even in the middle of a calm summers day with no wind-as the motion of bouncing alone will make then shift.
They should be staked with iron stakes deep into the ground and if tall tethered with additional ropes and stakes. Sometimes sand bags used as well.
It sounds very much like this wasn’t the case here and certainly with other recent tragedies and it’s absolutely horrific because it should never ever happen. Those poor children and their families.
When my kids go on one these days I do find myself checking the tethers first as sadly there are too many cowboys or people who simply don’t know what they are doing hiring them out.