I think they are quite constrained in terms of aircraft available ... THAT, and I THINK they wanted to start the route on a 'high' ... assuming that traffic would justify a 763. They are in talks with lessors for 77Ws ... 788s should come online some time next year (?).
as a side note: I remember that during the 80s and early 90s, Alitalia maintained a strong link with NBO
... even when it deteriorated to seasonal flying, one just needs to head to the North and South extremities of the Kenyan cost to appreciate the amount of tourists that were from Italy/West Germany and UK.
Apart from Tourism, as you rightly point out there is a rather affluent population of South Europeans living/working in E.Africa.
Now they are competing with Emirates, Qatar, Etihad, Ethiopian, Gulf Air, Turkish (Red eye flight) to name a few ... basically passengers will be swayed by price, even if it means a stop-over in the opposite direction (i.e. Stop Over in Middle East - assuming ME carriers)
I dare say NBO
is a strong market, hence the addition of all these carriers ... with what I feel EK
being the strongest, servicing NBO
with a double daily with a A332 and B772 during peak season.
Interesting times ...
There's Method in the Madness ...