Tri for whatever reason decided they wanted to fan the flames of shipping from the word "go" (it was showcased in the first PV) when everyone and their dog fucking knew it was extremely pointless to do because Mimi marries Michael*, not any of the OG DigiDestined. I don't know what they were thinking in deciding "Oh Izzy's crushing hard on Mimi now after all this time". That's why the ship got more popular, but pre-Tri, Joe/Mimi was the bigger ship among Japanese fans.
Mind you, Tri made a lot of dumb decisions, but that one's baffled me the most especially since it doesn't go anywhere at all. Mimi doesn't even give him a follow-up or rejection or nothing. But I mean, they dropped a lot of stuff, so what's one more.
EDIT: *It's a popular fan-theory, though I swear there was a kid clone in the epilogue had kinda looked like him. Mimi's son is ambiguous enough, I suppose, but she clearly did not marry Izzy or Joe, and the only other character who liked her was Michael, and she likes America a lot to have dual-citizenship it looks like. So it's generally assumed by the fans the two married even though Michael doesn't show up in the epilogue because only the main cast matters.