Without a proper airport diagram showing where the helicopter was parked, what was the clearance issued , and what was the actual flight track , the you are all speculating widely .
Normally heli routes do not interfere with dep/arr normal traffic ( low and perpendicular) clearances to x active are done by TWR controller, and a normally buildt controller will not allow a x during a take off.
there is something more ,( as usual) I'll wait until I see the R/T transcript and see the track .
For the SLFs here asking about " electronic protection" : helicopters are not required to carry TCAS and in any case TCAS RAs are disabled at those altitudes.