It certainly was politically expedient to draw as large a distinction as possible between their version of Christianity and the Jews, who had engaged in a series of costly and bloody revolts against their Roman overlords.
There is nothing new under the sun. Marcionism is alive and well in many quarters in the form of neglect or outright rejection of the OT, and-even worse-the neglect or rejection of the Johnnine books of the NT. The “Jesus Seminar” heretics took Marcion’s Canon to its logical conclusion, which is to claim that there is no canon.
Later.