The Left has been dominated by the political philosophy of Progressivism since about 1900. One of the principles of Progresive ideology and thought was the Constitution was obsolete.
A major problem of the Consitution was it deliberately limited the power of the government. Progressivism believed government power was an unlimited power to do good.
Therefore, the Constitution was an obstacle to do good. Ways had to be found to "work around" or ignore the Constitution to do what they wanted to do.
Woodrow Wilson was a major Progressive ideological thinker, writer, and proponent of Progressivism who later became President.
From Woodrow Wilson's Socialism and Democracy, 1887:
The thesis of the states socialist is, that no line can be drawn between private and public affairs which the State may not cross at will; that omnipotence of legislation is the first postulate of all just political theory.
Applied in a democratic state, such doctrine sounds radical, but not revolutionary. It is only an acceptance of the extremest logical conclusions deducible from democratic principles long ago received as respectable. For it is very clear that in fundamental theory socialism and democracy are almost if not quite one and the same. They both rest at bottom upon the absolute right of the community to determine its own destiny and that of its members. Men as communities are supreme over men as individuals. Limits of wisdom and convenience to the public control there may be: limits of principle there are, upon strict analysis, none.
BTTT
“…deducible from democratic principles long ago received as respectable. “
Oh, well, there ya’ go. Flawless argument there.