Why is that the highest bidder does not get the property ?

It’s not as simple as taking the best offer because the seller typically only sees one offer at a time on a property in the current market. A seller might reject an offer because they think they can get more .. but higher offers never materialize. A month or two later they sell, despite having rejected higher offers off the bat. It’s not as if all offers are received at the same time (as was more often the case in 2003-2005). Also, as mentioned above, the seller wants the sale to close and looks at indicators of the strength of the buyer (down payment amount, etc).