Most double legs in freestyle wrestling are from the knees and the head is higher because you don't need to worry about guillotines. Plus, your opponent obviously knows you're shooting as that's what you're there for. The GIF that TS supplied showed a nice drop-double feint, to clinch feint, back down to a driving, low double that he commits to.
In MMA, your head has to be lower or much higher to avoid the choke. Plus your opponent isn't JUST expecting the TD, so naturally they aren't constantly in a lateral feet position with their head low ready to sprawl.
What's strange is that you never see too many angle leg taps in MMA these days, where you drive in for a double, switch your direction 45 degrees and tap the knee for a power double. It's usually just power doubles to get them straight backwards to the fence and get the TD from there.
The best wrestler who replicates amateur wrestling techniques, especially with their chain wrestling, is Frankie. He is phenomenal at grabbing a single, and if he doesn't get the snatch TD, he immediately goes for a high double leg, and if he doesn't get that, he switches 45 degrees and drives for a power double. If he doesn't get that, you're usually on the fence by that point and then you have to defend his snatch double. It's no wonder he gets everyone down with relative ease.
