K-9 mail... isn’t supported or being developed any more.
That's not true. They make frequent-enough releases, they post monthly progress reports, and they are actually going to become Thunderbird's Android version.
Having said that, I almost switched to FairEmail because K-9 lacked support for some sort of authentication measure (which I no longer need), but that wasn't because K-9 stopped development.
Days before the 2016 election, 538 (which Nate Silver founded and was leading at the time) ran an article titled "Trump Is Just A Normal Polling Error Behind Clinton". Nate Silver and 538 did some of the best forecasting of that election. Don't conflate him with others' screwups.