Why athletes have higher cardiac output during maximal effort and lower higher rate at rest compared to non-athletes? why athletes and non-athletes have equal cardiac output during rest and equal heart rate at maximal effort?

The difference is the stroke volume which is much higher with athlete's heart. So when the heart rate at rest is lower but stroke volume is higher, cardiac output can be the same or higher in athletes. At maximal effort, stroke volume drops in normal people due to reduced diastolic time (very high HR) but stroke volume does not change much in athlete which explains the athlete's higher C.O.