Why did Leer cause the opponents defence to harshly fall?

Question

Harshly is two stages, right?

I’m playing SP and Chimchar used Leer, says it harshly fell. Isn’t that two or three stages when it’s supposed to be one?

Comments

Did the Pokémon have simple? Bidoof is common and can have simple.

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I was fighting first route bidoofs. Now I feel like an idiot thanks

Answer 1

Simple doubles the effectiveness of stat stages.

Source
Like AlphaSapphire said, it's the reason most likely. One of Bidoof's Ability is Simple and it's common in the wild, which is why Defense harshly fell.