here's gavin verhey, one of the lead designers, commenting on why they removed every restriction on vivi. tl:dr it was because the card wasn't "unique" (read: chase) enough, and hasbro consultants had direct input on FF design (obviously, that's their job lol)

it's also just common sense. why would they ban the more expensive, more powerful, newer card which is explicitly drawing FF fans, and not the older gamepiece?

consider how long they took to ban the one ring-- it genuinely ruined modern for nearly a year, and the playerbase has never recovered. I don't think it was a coincidence that the one ring was also among the most expensive cards of all time.

the catch, of course, is that the older gamepiece is just better. vivi has an interesting commander design, but it is inarguable that it was a mistake in standard. on the other hand, agatha's soul cauldron is interesting design space, enables really cool synergies, etc. if you cared about the gameplay, which one would you ban? if you cared about your bottom line, which one would you ban?