They are not JUST BUNCH OF APES MOVING THIS WAY TO THAT WAY.
They have done it in past "battling Iran Qatar etc.. and lots of men have done some fire fights in Afghanistan Pak border
The tomb/shrine of Prophet Muhammad S.A.W. Iis created for the security reasons you can read some history of these shrines/tombs.... just my personal thinking if they don't protect graves of our Prophet S.A.W and his companions. Or if those graves are available to visit. Shias will try toattack...