The game tries to match people whos armies are similar in brute strength. Sometimes that means your army will destroy, be equal to, or be annihilated by the enemy depending on their types of troops. You can always "pay off" an enemy to skip pvp, its a very minor cost.
Also you get crowns for losing PvP. crown = 4,000g or $. I don't care if I lose. I'll lose all day long so long as it gets me crowns. With them you can get upgrades, resources, ect.