I just now realized that the bounty systems is very similar to the bitcoin mining method for getting tasks done.  There can be multiple people working on the same mining job at the same time.  However, only the system that finishes first gets the reward.

According to a Quartz article on bitcoin mining

Or rather, some miners are rewarded. Miners are all competing with each other to be first to approve a new batch of transactions and finish the computational work required to seal those transactions in the ledger. With each fresh batch, winner takes all.