If you do not understand this fundamental interaction triangle, you will constantly lose to players with inferior mechanical skill.

Learning exactly how these three categories interact is the first step toward building a viable deck and predicting enemy movements.
The Fundamental Triangle
However, that same P.E. Here is more regarding tower rush look into the web page. K.K.A will be killed instantly by a cheap Skeleton Army (Swarm) because it can only attack one tiny skeleton at a time.

Every time you place a card on the battlefield, you must ask yourself: "Which part of the triangle am I playing, and what does the opponent have to counter it?"
Never build a deck with only one side of the triangle.Reaction time matters.Spells are the ultimate wildcards. Advanced Baiting and Archetypes
Bait decks are designed entirely around overloading one specific side of the triangle to exhaust the opponent's counters.

This high-level psychological warfare turns the simple combat triangle into a complex game of mental chess.
Unit CategoryStrengthsThe CounterThe HordeHigh DPS single-target tanks, Princes, P.E.K.K.AsWizards, Valkyries, Bomb Towers, The LogSplash DamageSkeleton Armies, Minion Hordes, Goblin GangsHigh health single-target units, Mini P.E.K.K.As, Heavy Spells The Evolution of Balance
The delicate ecosystem of the arena relies entirely on this three-way tension.

Master the triangle, and the trophies will follow naturally.