Well, not really. It's remembered vividly because he gave an epic speech at the Convention and he never really mended fences with Carter, so there was still bad blood going into the general election. But his actual primary challenge was listless to the point where he couldn't even tell reporters why he was running. He never had a real chance at winning the nomination.
He got off to a bad start, certainly, for many reasons--the Roger Mudd interview, the temporary boost to Carter's popularity during the hostage crisis, etc.--but starting in late March he did make something of a recovery, winning the primaries in CT, NY,PA, DC, CA, NJ, NM, RI, and SD. (Before March 26, all he had won was his own state, MA.) In the end, EMK got 37.6% of the primary vote to Carter's 51.1%, a quite respectable showing for a challenger to an incumbent president. https://en.wikipedia.org/wiki/Democratic_Party_presidential_primaries,_1980
They didn't get any coverage because most of them were irrelevant perennial candidates. The media might not take him seriously, but they would definitely give an incumbent senator's campaign some attention.Especially one who gets no media coverage. There were people who ran against Obama IOTL, but because they had no chance no one talked about them.
A sitting President will win their primary in a landslide unless they have done a terrible job and their approval ratings are low. IIRC the last President to ever have problems during the primary was LBJ, who had Vietnam as an albatross across his neck.