I have made a similar comment on the LGW to Doha. One reason is the shortage of long haul cabin crew until later in the year.
New entrants have been recruited but do not start training until late August/early September. This is because priority at the moment
is being given to Heathrow training courses. This is why LGW to Islamabad will resume in late October.
I also have heard that Gatwick to Manchester has also been providing good connecting traffic to the other Gatwick long hauls as well as to Islamabad so it may or may not survive.