A big value of XP, Scrum, Lean, Kanban and Agile in general is the decreased time to market and increased success rate.
What are the top perceived reasons for projects success then?
The book from Crisp 'Prioritera Fokusera Leverera' references two sources on the matter.
The Standish Group CHAOS report 2006:
The Harvard Business School
article from professor Alan MacCormack 2001 that lists:
- An early release of the evolving product design to customers
- Daily incorporation of new software code and rapid feedback on design changes
- A team with broad-based experience of shipping multiple projects
- Major investments in the design of the product architecture