Unfortunately humanity (including hiring managers) is extremely fickle so the reason could have been as simple as "You reminded one of them of someone who bulli

Unfortunately humanity (including hiring managers) is extremely fickle so the reason could have been as simple as "You reminded one of them of someone who bullied them in high-school, so they lied and said you weren't qualified." IMO, about a good 30% of the time when something goes wrong it's literally as stupid as this. Don't blame yourself if you were nice, not arrogant, and qualified. Just blame random chance, because that's the truest reason that exists.