Monday act really busy all the time is due to the fact that we are starting off another week immediately after the few days rest the weekend provides. Monday is great time has it determines how exciting the week must be. Even though I don't like that much it's day that must liked if we intend to kicks start a productive week.
May also don't seem to love that day again because they hate their jobs. So it's quite understandable why majority don't find that day as their least favourite day.