Abram is blessed because he is obedient. Not only he but his nephew was also blessed through Abraham. He went with Abraham and because of that, he too was blessed. They walked in the favor of God. Then when their blessing had become a barrier in their relationship - Abram gave Lot the first choice of the land so they could separate. Lot chose the choice property leaving Abraham with the land that wasn't as desirable. Yet the favor of God was with Abraham and not the land. Because the promise wasn't about land, but about the man.