The simplest explanation seems to be the oldest one, namely that the census has always had a pattern of undercounting minorities and overcounting whites (and this time asians), and very much tied to having a stable address at which one could be reached. (So if those wealthy enough to have 2 houses & receive a census form for each, or college students studying away from home, are more likely to be double counted).
Normally a lot of effort goes into reaching out to people who did not respond to household surveys, or were not associated with a household, and many of us will recall how the Trump administration refused to extend the timelines for the Census to carry out that work of doing so (and made more difficult because of COVID). (And also recall that the administration fought to include a citizenship question on the census, which was expected to lower the response). At the time it was pointed out that Trump's decisions regarding the census would more likely hurt red states because of the demographics, and so it seems to have.
https://www.npr.org/2022/03/10/1083732104/2020-census-accuracy-undercount-overcount-data-quality
------------------------------
Dennis Sweitzer
Principal Biostatistician
------------------------------