I don't want to make a long post really. I just want to point out something i've noticed and if you want proof/ details, go search google, because i really haven't got the patience right now.
Towards the end of last year, a few videos and photos of drunk Niall started to surface. In 2014 Niall was consistantly dressed in contrasting colours from the other boys when they appeared on the red carpet. He was almost always placed in the middle and asked questions much more frequently than during 2013.
Now, in 2015 Niall, who was previously known to be the happy-go-lucky kinda SINGLE guy, is known to have a fling with Melissa. There has been published multiple articles by multiple newspapers, several of them highlighting the fact that Melly might have had a bf on the time of the November-vine from a casino.
Today more articles about Niall was published, this time focusing on an IG comment (yes, seriously) that Niall left on Samantha Jade's (the act who opened for them in some shows in aus) saying it was great having her play on the tour or something like that. The headlines are something in line with "Niall romantizising Samantha Jade on IG" .
There has definitely been a push from MM and 1Ds PR to make Niall the person in focus, more so than he has been before.
During the same period of time, Harry, who has been called "the leader" of the band multiple times, and has been the "womanizer" in the media, has consistently tried to shed that image.
My theory is that Harry's coming out/ seeding/ hinting/ change of image has something to do with Niall's sudden change of image. Boybands are businesses and they have certain roles to fill, because they need to gain the most amount of popularity possible.
One of those roles have always been the womanizer/ young mingling guy/ leader -type person and since Harry has been filling that role till now, Niall has been playing the role of accesible fun guy, Zayn the mysterious one, Liam the underdog-success-story and Louis the sassy, but sort of irrelevant one. Since Harry wont fill the womanizer-role anymore, Niall has to do it. Not that he neccesarily agreed to, but the 1D PR team and M!M might have.
Niall is still in some ways the "accessible guy" because the woman he is linked to was previously a fan. In that way they sort of sneak him into the womanizer/ leader role he seems to be gaining.
Harry is also still somewhat portrayed as the leader and a womanizer in some media outlets, but in general, his bad reputation has begun to turn around. He is still supposed to be the inaccessible, kind of stuck-up cool-kid of LA, but he is slowly shedding his womanizer-role onto Niall, I think.