Why would anyone question that she is a real person? If you like her content, watch it. If you don't, leave. What's wrong with being an anonymous creator?
In short: sexism.
For further reading, see criticism of the "fake geek girl" meme.
> the negative impact of my tweets was amplified by the fact that I, a white, Western, male CEO of a key company in the Maker community
This guy was not low status by any definition.
The fact that he maintained a sustained slander campaign when he ostensibly had other priorities implies he felt that ‘exposing’ her became important to him, again a trait of insecure, low status individuals.