Maybe it's just a load of bad luck and businesses that compare badly to what else is on offer in Brixton now (including further down Coldharbour Lane opposite the barrier block where Okan and Banh Banh are). Pre 'Village' there were so few places to eat out that they could survive even if they were a bit shit. We went to Asmara years ago and it was OK but there were always other places that appealed more (and there are two Eritrean restaurants at Oval that are meant to be really good if that's what you're looking for)
The Dogstar has long been a pretty tatty and unwelcoming place. It might have had some atmosphere when it's rammed but it's not been a pleasant place when it isn't for many years.
Rum Kitchen - whole chain went under
Brewdog
closed a load of bars across London
Le Bab - there were suddenly 3 kebab shops on Coldharbour Lane. The largest/most restaurant like (Mezze Me) has survived.
NanBan I'm guessing lost focus after the
founder left. A lot of restaurants seem to have a lifespan - if they're not part of a chain when the owner tires they close. It was expensive and there are two other Ramen places (Koi and Okan) nearby.
PoW and Albert must have really suffered while the academy was closed (though it seems to have a busy few months of gigs lined up now)