There was no conspiracy that caused the demise of the Rotodyne. Yes, the tip jets were noisy. But the aircraft still required fixed wings and turboprop engines for cruise flight. The benefit provided by the tip jet rotor for VTOL operation of a commercial passenger aircraft was not worth the added complexity.
But the Rotodyne could naturally de-ice its main rotor blades with no extra weight penalty.
Sixty years on, manufacturers still struggle to solve the complexities and weight issues of that problem.