- As you said, concern about Covid diluted the vitriol in a lot of political threads
- In 2016, t_d was in ascendancy, and its members would flood other subreddits with their talking points. After that, sub moderators established stronger anti-brigading rules. In 2020, t_d was either banned or made private, I forget which.
- A lot of the highly charged flash points of 2016 were no longer that relevant in 2020: Syrian refugees, trans bathrooms, 'identity politics'
- 2016 also had 2 polarizing candidates. In 2020 only one was still looked at that way.