Is Third Party Vote Dropoff Evidence of Voter Fraud?

Stu Cvrk at RedState has yet another article promoting voter fraud conspiracy theories.  He claims that the drop in third party and write-in votes between 2016 and 2020 is evidence of voter fraud.  In particular, he claims that voting machines were programmed to declare third party votes needed adjudication, and then election officials declared these votes to be for Biden.

There is nothing unusual about the third party vote declining when an incumbent is running for reelection.  Consider recent pairs of elections when an incumbent sought first an second terms.

5.7% 2016 -> 2.8% 2020
1.4% 2008 -> 1.7% 2012
3.7% 2000 -> 1.0% 2004
19.5% 1992 -> 10.1% 1996
1.0% 1988 -> 19.5% 1992
8.3% 1980 -> 0.6% 1984

Thus in the last 40 years, third party total declined four times and increased twice (once by a trivial amount).  This shouldn't be surprising.  When an incumbent runs for reelection, the election tends to become a referendum on the incumbent.  In 2016, many voters disliked both candidates, so they voted for third party candidates or write-ins as a protest.  In 2020, Trump won back some disgruntled conservatives, while many leftists and centrist rallied to Biden to defeat Trump.

Another relevant factor is the strength of the third party candidates.  In 2016, the Libertarian candidate was Gary Johnson, a former two-term governor of New Mexico.  In 2020, they ran an obscure adjunct professor who didn't make any impact.  Of course, the huge jump in 1992 is largely explained by Ross Perot, a billionaire who spent a fortune to run a credible national campaign.

Also arguing strongly against this theory is that the decline in third party votes happened in every state (and probably every county as well) between 2016 and 2020.  Were the vote counting machines corrupted everywhere, regardless of location and manufacturer?  Note that vote adjudication is a manual process, so rigging this would require crooked operatives in tens of thousands of vote counting locations all across the country.  And if they missed any of them, the third party vote totals would be wildly out of sync with the rest of the country.

These theories keep getting dumber and dumber.