After Cardi B's now-notorious footwear attack on Nicki Minaj we can officially say that the two rappers hate each other, and it's not just a case of patriarchy trying to tear women apart.
According to Jason Lee of Hollywood Unlocked, the pair fell out over a Future feature that wasn't.
Future, Lee says, was originally on Cardi's Migos featured hit "Drip." However, Nicki made an ultimatum to Future: Either get off the track or get off their joint NICKIHNDRXX Tour.
Lee says Future chose the tour, and Migos were inserted in "Drip" instead. He also claims he has the Future reference track for "Drip" which would back this up.
After the fashion week shoe-throwing incident, Cardi called Nicki out for being a bully and for trying to have her blackballed. So Lee's explanation of what happened with "Drip" would fit into that.
As for Future ... if he really did chose his tour with Nicki over the track, it was the wrong choice. The North American leg of NICKIHNDRXX was pushed back about a year, likely because of poor ticket sales, and Future is no longer on it.