The NBfL (aka Borismaster) was a Boris populist idea to have a dedicated bus for London. Lots of the usual wiffle. Having a two person crew was never cost effective and two staircases were folly. Cancelling the Western Congestion Zone - more Boris populism that was very short sighted, as was his war on bendy buses.
If I remember correctly, Johnson won most of his votes in the outer London boroughs. Boroughs that didn't have bendy buses and would not get the Roastmasters...
Basically a bus policy voted for by the people who didn't use those particular buses ...