This pisses me off. It's open source, you can check yourself. If you can't understand the code, that's fine, just ask someone. Don't jump straight to accusing people of white supremacy with no evidence because you're bored.
The code is right here.
It searches for a high (today's score - yesterday's score), then, if that's the highest it's seen, takes that number squared and uses it as the trending score, halving the score every max_score_halflife. If the peak is older than max_score_cooldown, it forgets and lets it trend again.
max_score_halflife and max_score_cooldown are admin-configurable, but the defaults are 4 hours and 2 days, respectively.
Gaza isn't trending because the number of people tagging it is never substantially higher than were tagging it yesterday.