Franklin has some basic grappling, but Loiseau is good at defending it. A rear naked on a guy with good defence when you are wearning gloves, have at least one, possibly two, broken hands, a broken foot and you are wearing gloves is not that easy.
If you have a look at his fight record he has won a number of fights by submission, and did a pretty good job on the ground against Loiseau, as well as with the takedowns.