These players "trick" matchmaking in a way that they only update the minimum buildings required to build, research & transport their attacking troops. When you visit such players, you'll see that their bases have very low level turrets. Often only the minimum of 2.
Their HQ and troops will usually be only upgraded to a level where building doesn't take too long (usually below level 8).
With such an underdeveloped base they'll get low level match ups which they can kill easily with their much higher level (&number) load out. Often even without hero.
That way they can 100% their opponents in much less than 2min and when they optimize their load out (& maybe use bought crystals to speed the cooking up more) then they can reach a quite high attack frequency.
But.... this must be extremely boring.