I think the most obvious explanation is a lot of people were hired during a time of inflated valuations and those employees received stock option grants with incredibly high strike prices.
Now valuations have tanked over 50%. If this happened in the public markets, you would simply let the options expire rather than acquire the stock at a 100% premium (for example). For similar reasons, it’s probably not advisable to exercise options granted in the last couple of years in most cases, but that’s because valuations are likely down below the strike price for a lot of people.