NFL 4th and 10 conversion rate averages out to 30%
here
let's be generous and assume that those 3/10 are guaranteed wins. We'll come back to the 7/10 later
From the same source, FG% roughly 90. 9/10 scenarios are made field goal, 1/10 scenarios is equal to the 7/10 above
Ok, what does that mean?
For the decision to make a field goal to be better, the overall percentage chance to win has to be better than equal.
The benefit, of course, lies in only needing a FG to win in those 9/10 scenarios.
For all scenarios ending with a FG score/no score, we assume the Chiefs begin possession between the 15-25.
Assume Bills force a 3-and-out, which must have been a consideration in Marrone's decision to take a low-percentage play. Average a 40 yard punt, and the Bills get the ball on their ~30 with 2:00.
In 9/10 FG scenarios, approximately 40 yards and a FG are needed to win.
In 1/10 FG scenarios, 70 yards and a touchdown are needed to win.
In 7/10 Attempt scenarios, 70 yards and a touchdown are needed to win.
What you
must believe, then, is that it is likelier that the Bills would score fewer than 3 more FGs than TDs in these scenarios