David Greenberg
dissects the Republican obsession:
For the right, the fact that [Calvin] Coolidge presided over sustained growth—and without accumulating massive debt, as Reagan did—seems to ratify the wisdom of the low taxes, loose regulation, and limited government that they still champion. As for the Depression, they find it easier to scapegoat Herbert Hoover—almost certainly the worst president of the 20th century next to Richard Nixon—than to admit to blots on Coolidge’s legacy.
This view is problematic for many reasons, not least because it assumes that presidents neither benefit from the achievements of their predecessors nor bear responsibility for the long-term consequences of their own policies. Coolidge in fact benefited from the wartime spending under Wilson, which buoyed the economy into the 1920s. And while he can’t shoulder all the blame for the Depression, in retrospect many errors of his economics became painfully clear.