Rupert Candy wrote:

(I imagine providing access to the Dome from aforementioned areas also
had something to do with it...)

Surprisingly no - the Jubilee line was planned and well under
construction before the Dome was conceived. The Dome was basically
sited so as to be next to the Jubilee line (IIRC Birmingham NEC was
another proposed location).

Obviously once the Dome was confirmed for 2000 it then became critical
to complete the Jubilee Line in time - original completion date at the
start of construction was March 1998, but it slipped behind for various
reasons. The press tended to present the Jubilee line as being built to
serve the Dome, but it was never that way.