More understandable if you’re comparing, or discussing different airlines.
Flight Planning and weather/wind forecasting has developed significantly, so much so that it should be possible to accurately predict, based on the actual time of departure, where company aircraft MAY ‘share the same airspace’..that is, cross paths or remain in trail for a period, within +/- 2000 feet.
It has been well established that the adverse effects of wake turbulence linger for some time (i.e. minutes), usually sink over time, and can shift due to proximate winds, in this case upper level winds. A380 at close to maximum weight, such as a Qantas aircraft departing LAX for Australia, would create dangerous levels of turbulence. Further, aircraft in cruise and/or cruise climb are travelling at a speed which results in significant distance across the ground in the same period (i.e. at 450 knots, 7.5 nm per minute, x 3 mins for 22.5 NM). This would suggest a ‘gap’ of minutes and minimum altitude separation may not be that smart..
In addition, TCAS should assist to maintain SA regarding the proximity of other aircraft.
Probably just sheer luck that no one was injured.