According to this post from Stack Exchange staff member SpencerG:
Questions surrounding the Typst proposal encouraged us to examine the support for the proposal and whether it was being propped up by sock activity. When I examined the supporter activity, it became clear that around 55% of its supporters appear to be socks and exist solely to prop this proposal up.
Does "sock activity" refer to sock puppet activity?
Why would a person or entity want to use "sock activity" to push a proposal for a Typst SE? Who stood to benefit and how?