Because he pioneered MASS PRODUCTION. Prior to Henery Ford's time, manufactured goods that required many parts were assembled at at central location in a factory. This meant parts from all over the factory had to be brought to that central location for assembly and completion. This was highly inefficient.
The ASSEMBLY LINE to the rescue............
While many people believe Henry Ford invented the assembly line, that honor goes to Ransom Olds who produced the Oldsmobile. Olds’ assembly line was quite primitive though and very much a manual operation. What Henry Ford did was take Ransom’s idea and so greatly improved it by mechanizing it, that a Model T when first introduced in 1908 cost $850 but ended up costing less than $300 in the 1920s due to vast improvements in and constant honing of his assembly line, i.e., mass production. In 1927, the last model year of the Model T, the cars came off the assembly line at a rate of one every 24 seconds.
During WWII, Ford used mass prioduction in the war effort. His Willow Run factory ultimately turned out a B24 bomber every 63 seconds. It was a massive undertaking for a huge facility and it was completed in record time.
He was the captain of industry because he was the person who was solely repsonsibly for the implementation of MASS PRODUCTION by using a highly efficient, mechanized assembly line that did not exist before Ford's time.