barbell: Lots of squats (front and back) deadlifts, thrusters dumbbells: benchpress, rows, pushpress, arnold press, russian twists, swings lunges, push and pull ups, mountain climbers have no kettlebell so lot is done with the dumbbells.
90% rider, 7% tires/brakes/suspension, 3% everything else in a World Cup setting. Personally changing tires and adjusting to the limits of control is much more time intensive than swapping frames. Imagine doing that at WC level.
I'll say the bike is more important than the rider. When you're talking recent WC times - the bike definitely matters, rolling resistance/traction/braking on the tires matters - you cant extract the two at the pointy end. Then theres sponsorship - you have to get to the races - And if somebody with a big marketing budget and underdeveloped (shitty)...