Person did weeks of cardiovascular exercise but only on one leg through cycling, the other leg was sedentary

After ending the cardiovascular exercise they switched to weight lifting on both legs

Greater hypertrophy or muscle mass gain happened on leg that previously did cardiovascular exercise

https://m.youtube.com/watch?v=ffRGEDsqV9g

I am presuming "Cardiovascular" means medium or long duration exercise with medium or low intensity such that the primary fuel source is Aerobic metabolism