Cognitive dissonance is a hell of a drug. Otherwise intellectually sophisticated, seemingly self aware individuals will bend over backwards with all manner of facile equivocation to ameliorate the discomfort of the realization that a belief clung to at the very core of their self perception does not align with the blunt object of reality. Sometimes it is a crude denial of painfully obvious facts. People with a little more time on their hands will employ confirmation bias, desperate misdirection, and clumsy rhetoric to construct labyrinthine justifications not necessarily to convince others, but themselves.
It is fear of pain. The realization that you've been lied to/mislead hurts. Especially when you've invested time and resources. Perhaps the realization that you've been lying to yourself hurts even more, people will do anything to avoid pain.