SoftBank made a promise on $1.75B of loans to WeWork from banks and is legally obligated because the latter going bankrupt just makes it fall to the former. So

SoftBank made a promise on $1.75B of loans to WeWork from banks and is legally obligated because the latter going bankrupt just makes it fall to the former. SoftBank is likely to end up owning a significant percentage of the post-bankruptcy WeWork through a debt-equity swap, through which the company will have likely renegotiated most of its abhorrent leases (the overwhelming bulk of WeWork's debt was longterm lease obligations).