They’re decertifying the voting machines and not the election. The machines can’t be used in future elections. The reason that they give is that too many people had unsupervised access to the machines since election day.
This is just a tactic by Democrats to block audits and inspections of voting machines. Plenty of people have had "unsupervised access" to those computers before they were ever delivered to the Clerk's office, including assembly line workers who made the parts in China and elsewhere, truck drivers, and many other people.
The entire premise of testing voting machine software is to establish that the voting software, when installed on a computer, performs in the same was as the tested software. Unless you have a test process that can establish that the correct software, and only the correct software is loaded and running then you really have no idea what that machine is doing.
There would be no purpose in doing certification tests, and generating cryptographic hashes of the tested code if that process did not allow IT people to verify that the trusted build was the only code installed and running on the election system.
Nobody should be relying solely on "trusted" access to voting machines for security. If you study the history of election fraud it is almost always people who are already in the government who perform the election fraud.