I would like to propose the following original answer, BEZRAT HASHEM : Rashi in Genesis 1:1 states that originally it entered Hashems mind to create the world in the attribute of justice only, however, Hashem saw that the world could not exist if based on justice alone. He therefore proceeded with the attribute of mercy and combined it with justice...... (Please refer there for further details)(END OF QUOTE)

In order for Man to exist, he needs Devine mercy........This is a well established principle and concept that is readily understood and perceived................................................

When Mosha entered the circle, he was actually role playing and demonstrating before G-d Almighty the very concept as brought forth in Rashi 1:1.........Just as the world would not be able to exist only with pure justice , Mosha would not be able to leave the confines of the circle as well ,clearly demonstrating before G-d Almighty the confinement of the world if only justice without mercy prevails......................... Hashem saw Himself the inability of the world to exist with pure justice alone. Hashem understood in His infinite wisdom that without mercy the world would be narrowly confined and ultimately be unable to exist and function. Mosha by confining himself in a circle had demonstrated the need for G-ds ultimate mercy to be aroused.............. This was a very potent prayer in deed........................ We must also pray for mercy before Hashem, for it is surely needed for our very existance......Have a Good Shabbos............................................................