>>1969280As previous anon said, geometry matters a lot. On a bike where you're leaned further forwards you're in a better position to shift your weight around for handling, and are always able to put more force into the cranks when compared to a bike that you sit more upright on. But the trade off is that unless you're strong and fit, it's more comfortable to ride in a more upright position, largely because a higher percentage of your body weight is being carried by the saddle.
To your specific question, the reason why you can't just move the road bike parts onto the upright bike and get the same results are the frame geometry. The most important measures in this specific case are lines E/G. The upright bike is designed for slow and steady steering which works when you're sitting in that posture, but if you put drop bars on this bike it would feel like steering a boat and suck at anything but going in a straight line.
