the thing is Iris never died in the normal timeline. Prior to flashpoint Iris writes that article, gets married to Barry, they have kids etc. This only changes post flashpoint.
I think that Savitar kills Iris as a deep form of revenge for his incarceration when Barry creates flashpoint and unwittingly provides a means for Savitars return. It is because of this Savitar is able to go back into the past and set himself up in history like he does.
Prior to that I reckon Barry needed to make time remanants for some reason we don't know yet, or maybe we know and i donn't remember, initially the original time remnant is shunned because he's not Barry, he goes bitter and starts causing havoc. Barry fixes the problem trapping him. However, when Barry creates flashpoint Savitar ceases an opportunity for escape and freedom, involving Wally and killing of Iris is to bring Barry as much pain as possible.
Iris' death is not instrumental to Savitars original creation, but it becomes a key part to his post flashpoint creation.
- - - Updated - - -
no, Flashpoint changes things for the original Savitar, he meddles with time going into the present to kickstart his own creation under flashpoint and maximise pain for BArry.