Nicki features on songs by people less famous than Jessie all the time, and Jessie J is more successful than Ariana (and even Nicki) in most countries, so that can't be the reason. They just decided to all be leads.
She hadn't got a big hit since Price Tag in Europe and Alive flopped even in her own country
there's NO RULE about lead or features. It's just in label and artists choice if they do Jessie J, Ariana, Nicki oraz Jessie J feat. Ariana & Nicki. With Bang Bang label chooses all three leads, with Problem they choose Ariana feat. Iggy, but if they wanted, they could do Ariana & Iggy and no one would stop them. It's just their option how they write this and put on iTunes.
And Billboard count their number ones or Top 10s no matter if it's & or feat. everyone who is on the song and it's credtied - has number one.
with Wake Me Up or Low they count numner ones for Avicii and Flo Ride, but Aloe and Kesha weren't noticed so they don't have this number ones.
BW & Anaconda can both smash. My question was legit. I didn't understand the whole feature /co lead BS. No one is "seething" over Minaj "success" . The song hasn't even started to smash ..........yet.