Don't want to bump this up, but just a couple comments to the OP -
1) Wasn't Bruce Lee defeated back in the day? I know he was a phenominal fighter, but I don't recall him as not ever being beat. For whatever it's worth, I knew a guy who was into martial arts (obviously an older guy, reference time period) and he told me he'd seen Bruce Lee get beat. He said Lee was very, very good (duh), and what was most impressive was his hand speed. The guy (Jim) stated it was basically super difficult to keep track of his arms below the elbow - super fast fighter with lots of focus. He'd wathced him do the 3 inch punch or whatever. As someone already noted that comes from a strong base being able to use your hips, but also shoulder, which would be moot in many grappling situations.
2) Bruce could have learned more if he were alive today, but if you are saying the Bruce Lee from back then would beat everyone, you are wrong. Bruce was partly so good because of his enlightening interpretation of the martial arts, to incorporate all the arts, and focus on the best techniques from them. Still, I don't know if he incorporated much wrestling into his training, and I would say any great wrestler that could slightly distract him with decent stand-up would be able to get a takedown on him. At that point, the mma game of today (Damian Maia is an extreme case, but any top tier BJJ practitioner) would be able to submit the Bruce Lee you are referencing.