I'm not 100% sure about this but I think a market maker that agreed to buy those 1+ MM shares at a lower than bid price did not necessarily have to sell those shares to anyone in particular right then and there. They simply put those shares in their MM account and then sell them later to anyone interested in buying at the ask or higher.

When you or I sell our shares, if not a large block, we can usually get our buy at the current best (highest) bid price. But if we have a very large block to sell, the MM will only buy from you at lower than the bid.

When you or I buy shares, if not a large block, we usually pay the best (lowest)ask price. If we want to buy a very large block, the MM will make you pay a price at more than the current ask!