Flat earth is quite a rabbit hole for many people. I wonder if they are so wrapped up in it that it becomes part of their identity making it very hard to let go, to the point of being intellectually dishonest with themselves.

A few of the big players in flat earth are known to be dishonest. For example Bob Knodel who featured in the gyroscope experiment you mention was previously caught out lying about being an professional pilot (and his claim of being an engineer is probably also a lie). I suspect there are also a lot of people in it who are not really flat earther's but are doing it for attention/views, etc.