So to summarize:
Larry Sanger resuggested "WikiProject Intellectual Diversity", a group with the goal to make "Wikipedia more intellectually diverse" and "ensure fair and open decision-making and governance, broaden the range of permissible sources, reinforce genuine neutrality, rein in over-aggressive blocking while holding the powerful to higher standards of accountability", etc, with the implied undertone of preventing Wikipedia from drifting too far to the political left.
This is unpopular because people oppose this on various grounds (mostly that it might be vote brigading and tiling decisions in their favor just by showing up in an organised way around wikipedia). Also the same project was apparently suggested before and rejected in early stages
But then he made a tweet that basically just says "I suggested this, some people like it, some hate it". That's super against the rules, because it attracts people to the proposal who otherwise wouldn't have seen it. Probably in an attempt to sway discussion, because his tweets are obviously seen primarily by people who like his ideas
Which then lead to the vote to ban him from editing Wikipedia. With a total ban getting more votes than a more limited ban, like banning him from participating in articles namespaced for internal matters.
There are lots of comments about this news ... Some of them are quite entertaining !!
[Source]: YCombinator [ycombinator.com]
[Ref.]: https://en.wikipedia.org/wiki/User:Larry_Sanger [wikipedia.org]