I mean, "stealing" is a strong word. Elon bought them out, and they're both enjoying a net worth in the hundreds of million.
What's more disturbing about Elon's tenure as head of the company is how social media manipulation, insider trading, and blatant SEC violations can pump a company's valuation into the stratosphere.
Marc Tarpenning and Martin Eberhard both continued to contribute advances in engineering that far exceeded the Tesla project. But they'll never have the kind of easy credit Elon secured through politics and media manipulation. So don't expect to see them included among the ranks of "billionaire" any time soon.