Tā fā le nà tiáo zhēngyì shìpín zhīhòu diàofěn yíwàn duō.
After he posted that controversial video, he lost over ten thousand followers.
Tips
usage
Antonym of 涨粉 (zhǎngfěn, gain followers). Both work as transitive-style verbs even though Chinese morphologically treats them as verb-object: 掉了一万粉 (lost ten thousand followers) is grammatical.
memory
粉 (fěn), short for 粉丝 (fěnsī, 'fans', borrowed from English 'fans' via the noodle homophone). 掉 means 'drop'. Picture follower numbers ticking downward.