Have you ever wondered which promotions actually feed the most top fighters into the UFC? M-1 is an obvious one with how many top fighters come from the Russian MMA scene. As for the USA scene, it has been especially clear lately that the LFA has taken over as the #1 American feeder into the UFC.
You might be wondering what happened to some of the promotions you see that were successful feeders but have disappeared off the face of the earth (the ones shown in blue). The answer is mergers and acquisitions. WEC got bought out by the UFC. Legacy FC became the LFA. And RFA merged with Titan FC.