What do you define as "success," because Canada, New Zealand, South Africa, Argentina, Chile, and Bahrain are all pretty high up on the Human Development Index and were former colonies (or, in the case of Bahrain, a protectorate)
There are some really good answers to this and similar questions if you search "former colony" but the top comment [here] (https://www.reddit.com/r/AskHistorians/comments/499v1z/why_have_places_like_canada_australia_new_zealand/) is a good place to start