Trying to make sense of the constantly changing timetables of this period is difficult.In hindsight some of the decisions seem distinctly odd.
As you say it all comes back to a lack of aircraft and the failure of the Tudor was a major setback.
The Solents were leased from the Ministry of Civil Aviation and the Hermes was purely a stopgap.
Things did finally start to improve when the Argonauts arrived.
The Solent service to Dar es Salaam was in connection with the ill fated groundnut scheme.
I notice there was another short lived stop at Lake Nyasa on the Johannesburg service.