The CIA could easily infiltrate manufacturers of ASIC machines used by bitcoin miners and plant hardware-level backdoors/malware. 5-10 years later, the hardware is used by most miners. They could also assassinate Core devs.
The law could prohibit Bitcoin ATMs, and crypto exchanges could be banned, making on/off-ramps virtually non-existent, aside from the occasional hand-to-hand irl exchange. People could still get paid in Bitcoin but practically nobody would accept it (no network effect, no utility).
The fact that this didn't happen makes 2 things most likely — either Bitcoin poses no real threat to the financial system (unlikely I think) or it was created by the government in the first place. This theory is further supported by the fact that Bitcoin came out of the USA, and specifically at a time of an uncontrollable debt crisis. If it was intended as a debt-clearing tool, it also gives the USA a big advantage for adopting it before other nations. If you look into the people and companies who are pushing for its adoption — in Trump's administration and its proximity — you'll find many odd connections and perverse incentives.
Further reading:
The Bitcoin-Dollar: An Economic Monomyth — by Mark Goodwin