Uncertainity principle:
Well, Heisenberg was in a "rival" battle against Schrödinger. Both people had very different ideas on how the atom worked. Heisenberg had his uncertainity principle, while Schrödinger had his time-dependent equation (generally used form). At first Schrödinger's equation was popular. It was like similar to other physics equations, and Schrödinger was able to produce an actual image of the atom.
However, Heisenberg's equation was very different. He had proposed a completely new idea - that you could not know both the position and momentum of a particle at the same time. This was sort of a shock to most physicists - this type of thinking had never been seen before. However, Heisenberg's theory gained acceptance soon. Schrödinger's equation did not die out of use either as he was right too.
I think Heisenberg main motivation was to prove Schrödinger wrong. After all - they hated each other. Sorry if I'm spouting out nonsense - I'm only in middle school. But I'm pretty sure about the above. I know there is more to this that I may have explained. For example - Heisenberg supposedly came up with his theory when he was on an island when he was sick (I know - this sounds far-fetched). He also worked with Bohr a lot when developing his theories.
Anyway - hope this helped! :)