Fun video, but at least towards the end the population numbers don't seem terribly accurate. The video counts the population for the greater metro area of a given city (e.g., 38 mil for Tokyo), but there's no mention of Seoul. The population for the Seoul metro is 25+ million, NYC metro is 20+ million, Moscow metro is 20+ million, etc.
Where's Tenochtitlan? Low estimates are around 200k population before the Spanish came, which is above several other cities listed at the start of the chart race.
Cute visualization, but the data is sketchy and handling of modern megalopolises is really inconsistent. If greater Tokyo is currently in the top spot at 38M, then greater Shanghai and greater Jakarta (Jabodetabek) should be #2 and #3.
Tokyo was and other cities were firebombed to HELL in 1945. And ~~MILLIONS~~ (war-winners-numbers state 330,000 - but I suspect that number is not accurate, see: MacNamera's comments) were killed in the razing of tokyo and other japanese cities during WWII and not a single frame in that video shows a drop-back in population during WWII years.