My understanding was more that Coke Zero was originally targeted at men, who apparently viewed "diet" sodas as being for women. [0]

"We're positioning Coke Zero as a defender and celebrator of guy enjoyment."

It doesn't hurt that it's a chance to reformulate without people complaining about the change like "New Coke" (which was allegedly based on the Diet Coke of the time[1]) and so the Zero branding has likely expanded across the Coca-Cola lineup and other brands to expand that reach and introduce changes - and incidentally give them a chance to mess with their agreements with bottlers the same way as when they switched to high-fructose corn syrup [2] [3].

[0] https://hbswk.hbs.edu/item/should-mens-products-fear-a-woman...

[1] https://casetext.com/case/coca-cola-bottling-co-v-coca-cola-...

[2] https://www.google.com/books/edition/The_Real_Thing/jfGzHxGn...

[3] https://www.pressreader.com/usa/houston-chronicle-sunday/201...