"Knowledge is power" key to career success?

This is similar to the brain or brawn argument. Knowledge is power, but to get to the top in a career there are things like sheer guts, the ability to work with people. Learn to understand workers and use them to your advantage, or get the right person for the jobs you want to delegate. Emotional stability as you say - not getting hot under the collar when things get rough.

Most people I know either personally, or well known celebrities who have made it rich have done so through sheer hard work. Look at Richard Branson, he left school early so no college education and look at his success. Perhaps yes, know your market, know your opposition. But you don't have to be a scholar to be successful.

Even staying at the top requires more than knowledge. Add a little stamina and grunt to the mix as well.

I agree that knowledge is power, but it's not the key to success. If you have a lot of knowledge but you don't know how to use it, then you won't get success. To be successful in carreer there are still a lot of things you have to master, like how you communicate with your colleagues etc, not just the knowledge.