the Tet offensive was a new methodology to guerrilla warfare. It’s surprise and multi-faceted approach caught the SV
Army and US Army off guard. Yes, it ended in failure...sort of. It depends on from whose vantage point you are looking.
From the perspective of military campaign success it ended in failure as the SV and US armies ramped up and crushed them. From the perspective of the NVA they were able to administer a blow to the SV Army and the US, it also eliminated the VC as a competitor for power. A two-fer.
NVA had help from Cronkite
I was in Danang during the Tet offensive. I know what happened.