Whay are some people so successful and others less so?

There's no one fsctor to it. Instead, I'd say it's a mix of these factors:

1. Luck, probably split down into:

A: Genetic talent/skill B: Family/personal connections C: Timing/environmental circumstances

2. Determination, and the willingness not to give up early (may have a genetic component)

3. Hard work, and the skills developed from such

With no particular factor being able to guarantee someone is successful, but all of them potentially being able to tip the balance that way. It basically seems to be a bunch of factors that'll either click into place or not depending on your current situation and that of the world around you.

Luck. You need both the opportunity, and the know-how to be successful. The next Einstein won't do anything if his family can't afford an education.

Pretty much (if you want) you can trace everything back to Luck. FIGHT ME.