We cannot forget that this is a massive undertaking that is taking place to rebuild Jerusalem. The leaders have been established who be living there. Now they have to figure out who else is going to move there to help establish and begin to repopulate the city. A city without residents isn't truly a functioning city. So they make a plan that 10% of the people will move to the new city and begin to settle there. They cast lots, which was more than just like a flip of the coin. This was a process that they believed God directed and led the choices made. These people were not chosen by mere chance.
There could be different reactions to this process. How many people who were not selected felt sad that they were not going? Was it hard for people to leave their established homes to go to establish new homes? Like most things in our lives people may have had mixed emotions. Happy to be chosen go and be part of restarting the city. Sadness for leaving friends and neighbors behind. Excited for the adventure ahead. Sad for leaving behind what you have already worked hard to establish.