..an amalgamation of (most of) all the mentioned points.

"It seems to me that the biggest challenge of the PM is often to maintain espirit de corps and encourage the team members to own the project." aka FIFO.

"Minimise project creep" aka don't give the client a RollsRoyce when they asked for a Jeep.

Additionally provide a "shield" for the team to stop 'management et al' forever interrupting the team(s) directly with inane questions and directions.

The job of the PM is to ENSURE that the job gets done, ie the project runs smoothly and that includes "gofering" (making coffee and getting the first, and last, beers in if necessary).

Be lucky, be professional.