If you bled the brakes with a helper and the pedal got pushed all the way to the floor the master cylinder likely got damaged. Crud and corrosion build up in the lower halves of the bores where the pistons don't normally travel, then when the pedal gets pushed far enough the lip seals run over that crud and get torn. Professionals either gravity-bleed with no helper or they never push the pedal more than half way to the floor.