#1 Cardiovascular fitness is sport specific. Some have more carry over than others.
# 2 Cycling is more about endurance than strength. Bicycles have gears which gives you a lot of mechanical advantage and improves efficiency. Even weak people can cycle.
# 3 Cycling is very low impact compared to other sports. Chances of injury are very slim. Your highest chance of injury is if you crash, not when you just cruising along and riding at a normal pace.
# 4 Real life hardships and challenges is what builds mental toughness. A bike ride is a relaxing, stress relieving activity for me.