successful at vs. successful in

Here is a slightly different angle on the difference.
Successful at – is a generalisation, characterising the areas in which the subject is successful. For example, Billibob is successful at selling used cars.
Successful in – is a particular identified achievement. For example, Billibob was successful in his appeal against the prison sentence for misrepresentation.

Looking at the particular examples, I like at in the first – because I feel that this is a long complex initiative that is about changing attitudes and culture. It is almost certainly being achieved through countless smaller changes.
I like in for the second and third – because in each case there are very specific things that have been accomplished.

Reading Brioche’s comment again … I’m not so convinced this is a different angle at all – it could simply be a different way of describing the same sense of difference?