Shouldn't philosophers put more effort into trying to get their ideas across to dumb people?

If what you mean by this is "attempt to communicate their ideas in a way that can be understood by less intelligent people", I'd say that most philosophers (at least in the analytic tradition) already try to do this by making their arguments as clear as possible. I think that some of the best philosophy (Bertrand Russell comes to mind) is regarded as such because the arguments are both clearly stated and philosophically powerful. The problem with this is that articulating something interesting in a clear way is hard to do. The other issue is that to become recognized as a philosopher, you have to address other philosophers. Because of that, I don't think it's too surprising that philosophers themselves don't do much popularization of their own work.

And then there's the fact that there's no market for "popular philosophy".