• Increases concentration.
• Lets us stay in the moment.
• Helps us realize that our mind speaks, and then helps us silence it.
• By using both the right and left sides of our brain, it creates a state of inner balance.
• Helps us travel to our subconscious, find our troubles and solve them.
• Lets the artist break free from their obsessions.
• Calms the artist and makes them happy.
• Increases creativity.

Besides all that, I think the most important benefit of drawing mandalas is letting us keep away from screens and the complexity of everyday life.