The name was changed because of the discussion here:
What are the options for naming the Computational science proposal
which (according the voting at the time) was largely in favor of the name change due to the confusion with "computer science."
But, let's not split up this discussion. Carry on over in the other thread.
And by the way… if you really want "Computational Science" you're going to need a subdomain name. I wouldn't suggest "CompSci" for compsci.stackexchange.com. Even on Wikipedia, that name just redirects to "Computer Science" — which will just add to the confusion I alleged all along.