As per Dr Shiva Ayyadurai, there is a clear linear trend in Trump counties that show that the more republican a precinct votes the less votes go to Trump

In comparison, in Wayne County, the trend is as to be expected, flat with high dispersion

What is a natural explanation of the very linear trendline with low dispersion and the structural break at 20% Republican votes?

As, it looks like votes were taken from Trump the more the precinct and county went for Trump, because no one would look there
No one would care that Trump got 75% of the vote instead of 78%, so why not steal 3% from Republican areas
Fraud would only be looked for in heavy Dem areas