The phrase "marvelous job" means that someone has done really well at something. It indicates that the person's performance was impressive or excellent. Full definition
Seems our visual cortex et al. do a rather marvelous job of making sense of photon streams. (slaw.ca)
And when they say, «Oh yeah, now I know who this person is,» or, «Yeah, you're helping me understand it,» that's when the whole thing is just the most marvelous job in the world. (vanityfair.com)