Arqade is part of Stack Exchange, commonly abbreviated to SE. For many years, Meta Stack Overflow (MSO) was also used for questions about the entire Network of sites.
Eventually, this was changed. Stack Overflow got it's own, fresh meta site, and MSO became Meta Stack Exchange (*MSE).
Just on the topic of those specific edits: to prevent broken links, the devs ran a script which updated all the previous links to MSO to point to MSE (as per the edit history you've found)