Google has quite a bit of headcount in NY (12,000 now, up from 7,000 in 2018 according to the article) and at that current pace of expansion they could probably still use the space even if only a percentage of employees still work in office.
More importantly, this seems like it's mostly to hedge given that office building prices in NY are reaching new lows and they've already leased space in this building for a while.
I'm not sure that last part is true. The building hasn't been delivered yet. Google did announce the lease a couple years ago, but I doubt that lease has commenced as the building is still under construction.
That being said, Google does seem to snag big properties in a down market. They bought 111 Eighth Avenue back in 2010 around the financial crisis.
More importantly, this seems like it's mostly to hedge given that office building prices in NY are reaching new lows and they've already leased space in this building for a while.