There are many things that can stop the current bull run. If the USA or any country with a strong economy that influences the modern world does something bad to Bitcoin or bans Bitcoin, it will stop the bull run. If highly influential people like Elon Musk and Cristiano Ronaldo say something bad about Bitcoin, it will also stop the bull run. I also think that if any developed nation gets involved in war, it will stop the bull run. If Satoshi appears in public, this also might stop the bull run or might increase, I don't know. If someone sells a huge amount of Bitcoins, it can possibly stop the bull run because it will dump the market but I think a dump from a massive sale is only temporary during bull runs. Besides these reasons that I listed, I don't think there is anything other than these that can stop the bull run.