Apart from the factors mentioned above one of the most important reasons for innovation actually lies in the nature of human existence. Right from ancient times, man is an extremely curious species. We observe things that are around us and even assume things that are not. We thrive to understand how to attain things that aren't existent yet. I believe this nature of continuous curiosity both constructive and destructive gives rise to new inventions and discoveries.Apart from this, we had so many people inventing new things and devices, we needed the technology for all these wonderful devices to work together. So integration of several different inventions would be another driving factor in terms of technological progress.Also I believe the visionaries mentioned in the post worked really hard towards their technological expertise to expand the realm of the technologies they were working on so that they could inter operate and create something extraordinary. Essentially, even if the technologies they were working on didn't exist, they knew the potentials of it and hence worked hard to work towards realizing those potentials.