It may be that when doing push-ups, the posture is incorrect and the habit is biased to one side (to the right), resulting in uneven muscle growth.

The right hand is stronger than the left hand. When doing push-ups, you may inadvertently do it to one side.

When I do one-handed push-ups, I found that my right hand can do more than my left hand. I don't know if I used to lean slightly to one side when doing push-ups, but later I noticed it myself, which led to muscle imbalance between my left and right hands.