“the whole point with artcroll is that ashkenazi jews (and sefaradi jews) should be interested in learning about sefaradic gedolim (and ashkenazi gedolim)”
The whole point is that Artscroll is a BUSINESS that is run by Ashkenazim.
They know that books about Ashkenazim will sell. The formulaic Gedolim books sell. But books by/about sefardim don’t sell (as well). They did Rabbi Mansour and a haggadah because they would sell. Rabbi Mansour has some star power with his various internet outlets, and everyone appreciates the Hagaddah, the most widely published and commented sefer throughout history.
Furthermore, as Ashkenazim from Eastern Europe, they will work with what they know. Nothing against Sefardim, Temanim, Mizrachim, Yekkes, etc.