I have two points of clarification before I get into my analysis of this phenomenon:
-First, I would implore you to stop using the term “kung fu master”. Chinese martial arts are not a single monolithic entity; there are over 400 recorded systems, with huge differences in technique and curriculum. Further, “gong fu” refers to a level of skill, and not to the practice of martial arts at all.
-Second, to have this discussion, we must distinguish between the terms “martial art” and “combat sport”. While the term “martial art” is used generically in the West to describe any sort of systematic fighting, this is not correct. “Martial art” is not an original Western concept, but a translation of the Japanese term “bujutsu”; or as we would translate it today, “war techniques”. The term “martial art” describes training with weapons to survive on a battlefield. “Combat sport” is the correct English term to describe those systems of determining who is the better fighter under specified rules in a controlled environment–boxing, wrestling, kickboxing, judo (Japanese or Brazilian), fencing, etc.
The first thing to remember about Chinese martial arts is that, between the Boxer Rebellion and Communist Revolution, most of the real martial artists in China were either killed or fled. The “martial arts culture” of China today is mostly led by the students of lesser students and fakirs, or by government-regulated gymnastics programs (known as “wushu”).
However, I think that the outcome of someone trained strictly in Chinese martial arts being beaten in a MMA contest by someone who specializes in MMA is a foregone conclusion even without the 20th-century attrition, and I think my phrasing in this sentence explains why. But let us illustrate: take a 13th-century English knight, whose unhorsed combat specialty would be the broadsword and shield. Hand him a rapier and put him against a modern fencer in a fencing match. His wild swings and large target presentation would lose in short order. But, now let us take the contestants away from the constraints of modern law, and equip them with plate armor, shield, and broadsword. The fencer will find his poking attacks largely ineffectual, and his lack of familiarity with a shield largely fatal to himself.
This is equally true of Chinese (or any) martial arts vs. combat sport (such as the mis-named “Mixed Martial Arts”). In order to have a “system”, there must be an underlying philosophy of movement and technique which ties the elements of the “system” together. Further, between armed combat and unarmed combat, armed combat is without question the most likely to kill you. Therefore, the movement of all martial arts are predicated to the necessities of armed combat.
-Why do most martial arts keep the lead hand up and away from the head, with the rear hand near waist level–when anyone who boxes knows to keep both hands up protecting the head? Because that is how you use the most common of weapons–the big stick (whether you call it a “spear” or a “staff”).
-Why not specialize in elbow strikes like muay Thai? They are less common in Chinese martial arts for the same reason that they are much less common in the Thai martial art of Krabi Krabong–a sword can do much more damage at a much longer range, so it is better to specialize with that for the purposes of martial arts. Trying an elbow strike with a sword in hand is likely end with self-inflicted injury.
-Why not roll around on the ground like the Brazilians? After all, they have quite clearly demonstrated to the world the advantages of position and leverage offered by this specialization. In fact, Kodokan Judo would probably have evolved along these lines if Kano himself had not made rules against it. It is because, while those advantages certainly exist still outside of the controlled environment of the ring, they do not outweigh the fact that they leave you immobile, unarmed, and unaware of your surroundings. Perfectly acceptable in the most brutal of combat sport arenas, but a recipe for quick death in a battlefield environment.
The Duke of Wellington is famously mis-quoted as stating, “The Battle of Waterloo was won on the fields of Eton.” But you don’t send professional rugby players to win a war, and you don’t send professional soldiers to win a rugby game. If you want to succeed in the other specialty, you have to train for it, as well.