The AR is an inherently accurate design and can be made even more so with the appropriate modifications. The AR is a very popular platform for the accuracy chasers thus the market responds in like and fora dedications as well.
The AK is considered a workhorse kind of rifle, not as inherently accurate as the AR considering both designs in their base form. Certainly an AK can be made more accurate but the expense is greater, less options to choose from and in the long run one would still be chasing the AR in a dollar-for-dollar mod-for-mod race.
The AR is similar in market nature to the old Chevy small-block at the drags. It isn't necessarily the best engine going but it was the most popular. It responded well to modifications and could be modded by anyone, anywhere for a reasonable cost. Nothing else came close and the Chevy small-block went on to rule the day.