"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...
There was a period in which CCC experimented with sucralose instead of aspartame+acesulfame P, as I recall the "diet coke" got sucralose and the "coke zero" got aspartame+acesulfame P. But they went back to only one thing, and ditched the sucralose variant.
Artificial sweeteners are not sugar and only taste "exactly like" sugar to some percentage of the population. Hence all the different sweeteners. So count yourself lucky that pepsi zero does not taste awful to you.
First random article about it on google:
https://www.phillymag.com/be-well-philly/2013/08/22/study-fa...
More recently, I tried the Dr Pepper Zero and I like it very much as well. I have long been a fan of real Dr Pepper, but I just don't want that much sugar in my life. Diet Dr Pepper is gross, though I know people who like it. Dr Pepper Zero is close enough to the real thing that I don't feel like I'm missing out. I even inadvertently bought a pack of real Dr Pepper (the bottles are the same color!) a few months back and drank one without realizing I was drinking the full sugar version. That's quite a compliment to Snapple for their formula.