AS others have stated, Weidman, Jones and Rousey had extensive life long backgrounds and succes in wrestling, before switching to MMA.
BJ came out of nowhere, took up BJJ, became a world champion, went to MMA, and became only the second guy to win championships in two divisions, where one division was above his natural weight, and he took it from the then-goat of the division.
Although the others are amazing athletes, it doesn't really compare to BJ's crazy run!
Too bad he didn't have a proper work ethic. He could have been THE goat!
Fedor - Gustafsson - Machida - Jacare - Mousasi - Condit - Lombard - Pettis - Melendez - Barboza - Mendes - Barao - M. Macdonald - Dodson