Why is looking big seen as being stronger?

Can't a slim man have more muscle mass than an obese man? Why is looking big seen as being stronger?
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even when my body mass was 22, I was stronger than when my body mass index was 30. It was only fat what made me look big when my body mass index was 30.

Comments are so stupid really. A slim man who has been lifting weight for some time will lift heavier weight than an obese man who has never lifted weight in his life. That obese man doesn't even have what is called the begginner muscle gain since he has never lifted weight in his life.
Why is looking big seen as being stronger?
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