From what I am reading, its one reason and that is USD being out of flavor. Too much money printing, and COVID impact in the US, big boys are not keen on USD anymore.
HKD is pegged to US, so we don't generally see any moves.
A month ago, 1 GBP would buy you 1.25 USD. 1.25 USD would then buy you 1.25 * 7.75 = 9.6875 HKD
Today, 1 GBP buys me 1.30 USD which then buys me 1.30 * 7.75 = 10.75 HKD
UK hasn't done anything phenomenal to warrant an upgrade, Brexit drama still persists, or one could say, they avoided blindly following the Orange Man and that needs to be rewarded.