You do know that Michael Johnson was a college wrestler right? Healy was as well.
Shalorus was a wrestler who represented Great Britain in an Olympic Qualification tournament where he placed 8th
Trujillo was a four-time NAIA All-American wrestler.
Almost all of Johnson's losses are when he's taken down and controlled (off the top of my head Brookins, Jury, and Madadi, and Castillo was able to do it in the first round he clearly won, before the tko in the second). Trujillo as well hasn't demonstrated td defense that his background would suggest; he was tossed around by Tibau quite easily with no answer, when Tibau has been on the downswing (and Tibau wasn't the only one to be able to get him down multiple times). Kamal was on the downswing of his career unfortunately (he was up there in age), was surprisingly taken down a couple of times by Miller in the fight prior then went on to be taken down and subbed by RDJ and Aoki after the loss to Khabib.
They aren't slouches, but really Kamal is the only one that has demonstrated good td defense, but that was in his WEC career, since leaving there he's had problems and hasn't looked too good (he did pretty much abandon his wrestling to sprawl and brawl in MMA though).
Pat Healy is a better answer, but Khabib had a lot of trouble getting him down, only doing so at the end of the first two rounds, before getting a tired healy in the third in the middle of the cage. Healy was able to get back up without much trouble after other attempts and even got Khabib down once.
The lightweight division isn't exactly filled with good defensive wrestlers like 170, 145, 135, and 125, so it's not really Khabib's fault that he hasn't fought many.