That's a highly partial view of the influence of London mayors on TfL operations. I'd like to highlight some (by no means all) of the things that Johnson did which impinged on TfL operations, NOT in any particular order:-
A) Getting rid of bendybuses (this, admittedly, was a feature of his manifesto, so could be said to be done with public approval)
B) Commissioning the building of the 'New Routemaster' bus and signing orders for hundreds of them (again using the manifesto, but this time as a smokescreen when it quickly became clear that hop on/hop off was NEVER going to be reintroduced except in the most limited way and, even then, for a very limited time)
C) Pushing for the extension of the Northern Line branch from Kennington to a derelict site in Battersea that wasn't on TfL's Top Ten list of new Underground projects, that quickly gained approval
D) Refusing to sanction the extra train services to Bellingham that had been agreed as part of the undertakings around the withdrawal of the South London Line
E) Jumping on the Joanna Lumley bandwagon, together with George Osborne, over the Garden Bridge fantasy, which has cost London Council Taxpayers dear
F) The Emirates skilift
G) Agreeing with the Treasury to phase out government subsidies for TfL's public transport operations almost as soon as he knew he'd be out of office
Even the so-called Borisbikes were a Ken Livingstone initiative that Johnson was happy to glory in, aided by his cheerleaders at the Evening Standard.
The elephant in the room which is conveniently (for him and his administration at the Shard) never mentioned is, of course, Crossrail and who knew what before Khan was handed that particular poisoned chalice immediately after his own election. I don't believe for one second that Johnson didn't know everything was not hunky dory.