Why not just give the $700b to healthy banks so that they can lend to businesses and credit worthy consumers? If we have $700b to give, why use it to buy up to

Why not just give the $700b to healthy banks so that they can lend to businesses and credit worthy consumers? If we have $700b to give, why use it to buy up toxic debt? I understand wanting to keep the markets moving, so why not address the problem there?