There are a couple of things about the fight in question I would like to point out:

1) Lefebvre (is that a real name?) has been using CS since his first fight and has beaten both SiO (the weaker counter) and FF (the stronger counter).

2) He only has only one loss to a fighter under 260.

3) Martin has beats bigger fighters with FS and PG - he has only beaten 2 fighters over 260 with wrestling or striking styles, both with GnP.

4) Martin loses to bigger fighters with other styles - he has lost 6 times to fighters over 260 using various striking or wrestling styles.

Lefebvre's stats for CS suck, but that doesn't seem to matter. Good hidden stats + weight advantage = tough fighter in the lower orgs. Your guy Martin is pretty well trained and pretty well managed but his hidden stats are nothing special and he's tiny.

Martin's record raises an interesting topic though - are weight differences more significant for some styles than others?