I'm sure it contributed, and that is why Madam Hillary Benghazi accused Jill Stein in 2016 of costing her the election, but the main culprit was VOTER FRAUD - mail in ballots, rigged voting machines and crooked poll workers.
I agree that there was an organized election fraud effort that consisted of many fraud vehicles— vote switching in computers, purposeful calculation errors, destruction of Republican mail-in ballots, fictitious and dead voters, etc.— but, theoretically, making it difficult for a third party to get, say, 10K more votes in a given state if it were on the ballot instead of having to rely on write-ins, means the cheaters would have to get 10K more fraudulent votes in a state, which they may or may not have done successfully in a state where the vote margin between Biden and Trump was close.
And that is why things were made so tough for the Green Party.
The other reason why things were made so tough for them is that the precedent was set to restrict their access to the ballot so that going forward the Green Party cannot develop as an opposition party to Demonrats.