I'd argue that the Atom core itself could compete - it hit pretty much the same perf/watt targets as it's performance-competitive ARM equivalents.

But having worked with Intel on some of those SoCs, it's everything else that fell down. They were late, they were the "disfavored" teams by execs, they were the engineer's last priority, they had stupid hw bugs they refused to fix and respin, they were everything you could do to set up a project to fail.