1) A 37 yd FG isn't automatic, especially when the 2nd year kicker's only had half a season worth of starts; HE was on the road against a division rival, too (but handled it well in the end.)
2) Even the worst case scenario of KC getting the ball at their own 22 wasn't the end of the world with their mediocre one-dimensional offense against our excellent verstaile D. It's very likely they end up punting back to us after a three-and-out there, and even a decent return puts us right back near midfield, nearly close enough to try a FG ANYWAY if we find ourself in 4th and long.
In the event, our D committed a series of huge penalties before finally giving up a 34 yd TD run to Charles, but there's a good argument all that was because our many quick punts had tired them out, which is just another reason trying to extend a drive on 4th and 1 was a reasonable choice. As far as "conservatism," the history of all NFL plays says going for it on 4th and <6 ANYWHERE scores more points than a punt or even FG: Whether he knew it or not (and I can't read his mind,) KUBIAK WAS GOING WITH THE ODDS ON 4TH AND 1.