TFA suggests these companies hold large amounts of commercial real estate as long-term investments, so “let the lease expire” is likely not an option.
EDIT: And if they DO own it, it they would probably prefer to pay some rental management company to rent it out as office space for passive income rather than fill it with their own expensive employees.
A small part may even be that they value work done in-office more than work done remotely. But just pointing out it’s not the most plausible objection to remote work.