Front kick works well in mma right now, because it is underutilized, just like how jab was about a year ago. When an effective technique is underutilized, then people train less counters or defenses against it, therefore they work for the period of time, until everybody adds it to their game. Remember how godly jiujitsu was 15-20 years ago, and now it is less effective in fights (compared to 20 years ago) since people train submission defence as a daily part of their mma training routine.