I suspect that these big corporations were advised by banks and the government to scale back work from home policies to avoid triggering a real estate market collapse in cities by vacating expensive office space en masse. This could cause defaults by landlords and a housing crisis as workers no longer need to pay premiums to live near offices. An exodus from cities would crater housing markets, which would severely damage the overall economy. Thus corporations are only half-heartedly pushing for office returns to avert an economic crisis, despite the cost savings of remote work