I don't think a PR for Meb today was surprising. He had solid training and ran to win. Combined with great temperatures and little to no wind, he set himself up the best way he could.
I like the point that someone previously brought up about the overall course profile. It is easy for elite 2:04-2:06 marathoners to let him go and think they will reel him in later. In their mind, the calculated risk was worth it. Except that Meb took away on the easy sections (relatively downhill and flat). If they wanted to reel in the gap, they had to make serious moves and cover FAST miles on the toughest part of the course. It is one thing to put in a few fast miles, but not on the hills. Wilson Chebet was clearly laboring from the effort he made solo.