Approx. 68% of all projects fail at least to one of three target values of project success (time, cost, quality).
(Chaos Report 2009)
The ten knowledge areas of the PMBoK (Project Management Institute, 5th edition) are fundamental to prevent such failure. People-related issues play an important role. Think of Communication Management, Stakeholder Management & HR Management. But for all other subjects it is: Keep an eye on the people involved. (see also: "Peopleware" by Tom DeMarco)
So it doesn‘t matter whether you run agile software development (Scrum) or according to the classic waterfall model.
The mastery of the 10 Project Management knowledge areas and the orientation of the people involved will put you in the range of the 32% of successful projects.