That's a lie but it is a widely-believed lie and therefore impervious to the truth. State legislatures "make final decisions in any controversies over the appointment of their electors. ... Decisions by states’ courts are conclusive, if decided under laws enacted before Election Day."
Hypothetically, a state legislature could decide that winner-take-all allocation of electoral votes violates the 14th amendment. Hypothetically, the state court could uphold that determination and the Supreme Court could sustain that decision. This probably won't happen because it would be a break with precedent. But it could happen. It won't happen because it is more important to preserve the appearance of the legitimacy of institutions than it is to defend the integrity of those institutions. But to presume it couldn't happen is to foster the lie that there is no alternative because it is more important to normalize deviance than to admit the truth that the institutions have lost their legitimacy.
Remember what the Supreme Court ruled in Bush v. Gore? Many people considered that decision to be a politically-motivated legal travesty. If state legislatures, state courts and the Supreme Court were to throw out Trump's presumptive winner-take-all Electoral College victory on the grounds that it violated the 14th amendment, many people would consider such a decision to be a politically-motivated legal travesty. See the difference? The first happened -- the second, presumably, will not happen. That is the only difference.
On normalization of deviance from the University of Chicago Press, Chicago Blog:
The sociologist Diane Vaughan coined the phrase the normalization of deviance to describe a cultural drift in which circumstances classified as “not okay” are slowly reclassified as “okay.” In the case of the Challenger space-shuttle disaster—the subject of a landmark study by Vaughan—damage to the crucial O‑rings had been observed after previous shuttle launches. Each observed instance of damage, she found, was followed by a sequence “in which the technical deviation of the [O‑rings] from performance predictions was redefined as an acceptable risk.” Repeated over time, this behavior became routinized into what organizational psychologists call a “script.” Engineers and managers “developed a definition of the situation that allowed them to carry on as if nothing was wrong.” To clarify: They were not merely acting as if nothing was wrong. They believed it, bringing to mind Orwell’s concept of doublethink, the method by which a bureaucracy conceals evil not only from the public but from itself.