The banker had negative feelings towards the jurist. In the story, the jurist did him some not so good things. We would expect that the wager was done out of hatred for the jurist. The banker wanted to take revenge aginst the jurist.
The king sends people to the arena because he thinks that if they chose the right door (the lady) they were good people but if they chose the wrong door (the tiger) they deserved it and they were bad people.
