Re mo pushing the pace:
He did take the lead several times over the last 3k, but Kam just darted back up. He certainly wasn't just tucked in/checked-out... he was racing. I'm sure he knew he had the race in the bag when he saw how the kenyans reacted.
And lets not forget that mo was tripped up a couple times the last two laps and still defeated a guy that recently demolished everyone at world XC and has run a 58 half. Todays race was very impressive for the top 5.
Re weak fields:
As far as the slowish PRs, there are very few 10Ks held in cool weather. The championship races mo has won have included many runners with sub 3:35/12:50/26:50/60....the paris 5k a few years ago had , what, the fastest times for 3rd-7th places
While track is certainly weaker than it could be, with lots of talent going to the roads, its still very competitive (in the sense that tons of east africans attempt to become professional runners and there is a well established development system).
As far as the GOAT debate, i think it is still clearly Haile or KB, and will be unless Mo doubles again in Rio or sniffs their PRs (or even just pulling off a few shocking/dominating wins by crushing a good field from way out). Mo has tons of medals, two 3:28s, a good half and a pretty good marathon for cryin out loud.