Well, I don't think an anti-crypto law would be developed and passed promptly, but that's also not necessary for widespread change of sentiment on the market. Trump is quite unpredictable, so him making a 180-degree turnaround and saying something against Bitcoin would do the trick. Or a crash of a major exchange. Both are somewhat realistic, but not very likely. That being said, bull markets don't tend to last long, and it can just stop without any significant trigger, simply because of running out of FOMO fuel, so to speak.