My prior, as well as conventional wisdom, would be that charities run by people with local and cultural understanding of the areas in which they operate would have the largest impact.
This seems not to be the case, judging by givewells recommendations.
What would be your best guess to why western founders can expect to do well on eg. regional problems in India?
Valid point, Mathias. Our goal is to recruit founders with an EA-mindset from around the globe. Understanding the local context is a clear plus in this regard. We would, however, not trade that for other values (e.g. unwillingness to focus on cost-effectiveness). Of course, that mindset is not limited to a particular region. In general, we believe in a balance between an outside perspective (i.e. a fresh pair of eyes) and a local perspective (i.e. that offers valuable contextual knowledge).
In addition to being linked to a co-founder with local knowledge, it can also be helpful to rely on staff or partners who can add local knowledge. I have personally learned tons from fantastic colleagues in Nigeria.