Given that it meant the A380 stand had to be moved to Pier 5, which required the resurfacing of the taxiways leading to it and the stand itself to be completely rebuilt, plus the rerouting of an entire taxiway around the new extension, plus the extension itself, it’s not exactly a small and inexpensive project.
Aside from closing entirely, I’m also not sure what more you expected Gatwick to do? All but about 4 stands were completely closed at the height, everything else was switched off. The majority of infrastructure is still switched off. At the current traffic levels, Gatwick is going to struggle to pass 10 million passengers this year, which will mean two years at less than 25% of 2019 figures, and around 70 million fewer passengers than expected over that period. That’s a lot of lost revenue.