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I will add a few more: Make lots of money and join elite club, To help the needy, To make your people happy, To get yourself out of misery, To have some pleasures for yourself. I hope I haven't duplicated the motives.
So, which of these push you and how much?
However, I don't expect any of these two new languages to have the same rapid growth Java had. It just started in 1996 and there was an enterprise ecosystem built around it by 1998 (EJB, Servlets, JDBC) and ruled for about 2 decades already.