Krygios is the most unpopular player on the tour.
I've never met a person who claimed to like Krygios.
And Jordan Thompson's match with Fognini had a louder and more enthusiastic crowd than Krygios' match.
Jordan Thompson is not well-known, and still got more crowd support than Krygios.
Also, the 2019 US Open broke the all-time attendance record, and Kyrgios only played 3 matches, so he's a non-factor.
The other thing I'll point to is the fact that Krygios hasn't made a slam QF since 2015, and that means hardly anyone knows who he is, because the QF, SF and F of slams are the matches that get publicity.