#2 Because the match itself was a dud
I never get the idea of making people involved in a feud to team up before a big match actually takes place at a pay-per-view event. Which sadistic authority figure wants to see how three women that hate each other will be able to coexist with one another? Well, for whatever reason, WWE booked Flair, Lynch, and Rousey against the Riott Squad on this week's show.
Of course, there was no chance at all that The Riott Squad was going to win. So what if they're a cohesive unit taking on a makeshift team of women who've just come together only a while ago? There is a pecking order in WWE and that has been maintained in the lead up to WrestleMania 35, unsurprisingly.
Corey Graves deleted his Tweet! More details HERE.
The brawl had to break out because the match in itself was nothing. Something major had to happen to make the segment worthwhile.