Their business model seems to be selling short term leases and buying long term leases. This is all fine and dandy as long as they can find enough buyers for the short term commitments, but the distribution of almost all such strategies tends to be heavily tailed. You basically collect a small but consistent margin and occasionally suffer heavy and unavoidable losses.
That's a perfectly fine strategy if the company can stay solvent during the loss, but this seems far from certain in case of WeWork.