Simple their alliances suck and they cant figure out why, 99.9% its leaders who think they know everything forget its a team effort.
Another is too figure out your war strategies along with no other reason but too join disrupt alliances.
They wait until you load them in wars then attack out order, take easier targets screw lower players from having a chance get 5.
Most time the attacking lower plyrs not working with strategy doesnt work alot, if alliance has strong top and mid corp of attackers.
Spys wouldnt need to be sent out if alliances would stop having leaders playing God, realize the way their loading matches falls on them.
Their is no special secret too being in top 20, its consistency too working from same plan. Communicate and work as a team if plyrs dont follow plan make room for plyrs who will.