According to Manuel García, it was the latter. You can read how the idea occurred to him here in an address he gave to the International Medical Congress in London in 1881. In point of fact, García wasn't the first to devise this type of instrument (see here and here), but was the first to use it to divine the inner workings of the larynx. Was that a big deal? Certainly. His investigations opened up a whole new area of medicine and originated the field of voice science. Researchers are still building on his findings.