particularly what LchChester says above.

A huge amount - the overwhelming majority - of 77W long-haul arrivals are early morning. Then, a few more long-haul arrivals trickle in throughout the day. A few more long-haul departures trickle out throughout the daytime. Departures pick up a little in the early evening. Until finally, late night, there is another huge slam of 77W departures within a few hours.

Because the majority of long-haul missions don't depart until late night, there is quite a bit of "slack" in the early morning, ebbing and flowing throughout the day, and finally it gets pulled tight late night. Hence, during the daytime CX tries to deploy the 77Ws around Asia to keep the frames utilized, and tech issues in those outports could have a knock-on effect for the late-night departures because that's when slack is the tightest.

CX's 77Ws departing HKG late night (some depending on day of week, I actually counted 13)

LHR (x2)
SFO
LAX
YVR/JFK (CX888)
FRA
MXP
FCO
AMS
ZRH
CDG
JNB
MAN