One of the primary reasons for removing cars from Market Street was keeping buses and street cars moving. There was a huge citywide program to make buses faster, and many routes converge on Market St and travel some portion of it. The routing, including overhead lines, makes use of all four lanes. Cars slowed things down tremendously.

Advertising the move as an anti-car policy was just convenient politics. To a lesser extent that was true of promoting it as pro-bike. Market St was built for trolleys and is still the most important artery for trolleys, and that's simply not gonna change. Any serious pro-bike policy would dedicate entire streets to biking (Mission St would be perfect for this), but for some reason nobody advocates for this. I think the pro-bike lobby is more interested in making the city hostile to cars (and now buses) than it is in making the city convenient for biking. (There may also be some esoteric legal and budgeting problems with dedicating entire streets to bikes, but you'd think those would be surmountable if addressed with the same kind of zeal the bike lobby has for poking everybody else in the eye.)

The pedestrian criticism makes no sense. Market St feels infinitely safer to cross without cars zooming up and down with confused and erratic drivers. The emptiness is entirely a product of the office exodus.