LED bulbs are a relatively recent invention, thus their manufacture, at industrial scales, was built on developments in manufacturing engineering that didn't exist when the incandescent bulb was developed. So here's a question for you: if we went back and re-tooled incandescent assembly lines for modern processes, would LEDs still beat them?
https://www.energy.gov/eere/articles/study-environmental-ben...
I think this is easy enough to find though... maybe they just don't know how to find this stuff.