No, CloudFlare doesn’t use lava lamps to generate random numbers, that was a marketing stunt. Using a camera in a completely dark room is a better source of entropy than one pointed at lava lamps.
Also, nobody is saying that computers create a number out of nothing. The environment is a great source of entropy (temperature fluctuations, user inputs and so on) which are then expanded into a larger amount of entropy through CSPRNGs.