my best guess is that at least part of the spiking absolutely must be caused by US-based users - they don't report anything that would let me quickly figure out whether they only tracked US geotagged tweets, english-language tweets (i think this is unlikely given the tweet tracker they linked), or all tweets with no filter for languaguage or geotagging; but i do know that at that time of day, US users form a sizeable portion of the twitter population who could type 'nazi' (as opposed to twitter population who use other writing systems like chinese and arabic, which is also a huge part of twitter but generally wouldn't be in 'nazi' search results)

/overthinks everything more than anyone cares