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.
The king built the arena to show the people justice and dive them a properly of what would happen if the committed a crime. This will determinate if the accused was innocent or not, there were two doors, behind one was the lady and behind the other was the tiger, if the accused was found innocent he married the lady, if we guilty then he would be killed by the tiger. The king sent the accused to the arena because there they would proof they were either innocent or guilty.
