From the comments on this answer https://meta.stackexchange.com/a/391625/136010 it is suggested and agreed by staff that the chnage in May 2022 was the role out of a proper cookie consent form. If you don"t have performance cookies SO can"t work out the analytics.
Fro staff member Catija
"@JourneymanGeekOnStrike Yeah, if you go back further, the "traffic" numbers see a 40M/week drop between April and May 2022, which is when the cookie tracking changed, and then normalizes again until December. So, prior to the cookie changes, traffic was about 140-150M per week. But, to be clear - this is stuff we're aware of and have "corrected" for, I guess."
"@JourneymanGeekOnStrike Yeah, if you go back further, the "traffic" numbers see a 40M/week drop between April and May 2022, which is when the cookie tracking changed, and then normalizes again until December. So, prior to the cookie changes, traffic was about 140-150M per week. But, to be clear - this is stuff we're aware of and have "corrected" for, I guess."