Meat science is an actual scientific discipline. It even has its own university degree programs, associations, conferences, and a peer-reviewed journal (Meat Science). Meat scientists devote their careers to understanding how meat is produced, prepared, and preserved. Smithsonian spoke to several of them about how to grill the perfect steak. From Smithsonian:
From a flavor perspective, in fact, the differences between one steak and the next are mostly a matter of fat content: the amount of marbling and the composition of the fatty acid subunits of the fat molecules[…]
Flavorwise, cooking meat accomplishes two things. First, the heat of the grill breaks the meat's fatty acids into smaller molecules that are more volatile — that is, more likely to become airborne. These volatiles are responsible for the steak's aroma, which accounts for the majority of its flavor. Molecules called aldehydes, ketones and alcohols among that breakdown mix are what we perceive as distinctively beefy.
The second way that cooking builds flavor is through browning, a process that chemists call the Maillard reaction. This is a fantastically complex process in which amino acids and traces of sugars in the meat react at high temperatures to kick off a cascade of chemical changes that result in many different volatile end products. Most important of these are molecules called pyrazines and furans, which contribute the roasty, nutty flavors that steak aficionados crave. The longer and hotter the cooking, the deeper into the Maillard reaction you go and the more of these desirable end products you get — until eventually, the meat starts to char, producing undesirable bitter, burnt flavors.
The challenge for the grillmaster is to achieve the ideal level of Maillard products at the moment the meat reaches the desired degree of doneness. Here, there are three variables to play with: temperature, time and the thickness of the steak.