-I found it hard to believe that the trades Bane made in Bruce's name would have been upheld for more than three seconds. First, Bruce wasn't there; security footage can confirm that and Alfred could provide an alibi about his whereabouts. Second, the trade happened after the exchange had been taken hostage and everything had stopped. Wouldn't that look suspicious to...well, anyone?
They address that. Fox says they can prove fraud but that would take time. Enough time for Bane to do what they wanted to do (which Bruce didn't know at that time). Wayne Enterprises was already in trouble anyway, and the weeks it takes to settle this are enough to destroy a company. So better to be safe than sorry, they gave the company to Miranda Tate.