This article helps explain why Keys did not see sugar as a likely contributor to heart disease risk based on the data available to him at the time (addressing some of the incorrect claims made in the article linked to in the OP): http://www.truehealthinitiative.org/wordpress/wp-content/uploads/2017/07/SCS-White-Paper.THI_.8-1-17.pdf Today, the correlation between per capita national income and CHD deaths among industrialized countries is precisely the reverse of what it was in the 1950s. Japan and Southern Europe are now both much relatively richer, and Eastern Europe, the Caucasus, and Central Asia now have a much higher CHD death rate, while the U.S., Australia, and Northern and Western Europe have a much lower CHD death rate. It made much more sense to attribute the vast majority of CHD death risk to saturated fat consumption in the 1950s than it does today. When the data changes, it is understandable why conclusions may change. You can't know what future evidence may appear to subvert your hypothesis.