I got paid helping someone set up their rig close to February. Even back then the whole crypto space was very heated up.
It can't be said in a definitive way that ASICs are the primary reason difficulty has increased back in January timeframe. Especially when the so-called ASICs are very underwhelming in performance, price, and power consumption. The Monero ASIC doesn't count because the Antminer X3(the ASIC for Monero) does 100 times better in performance.
Time delays always exist. Shortly after the peak profitability is over, there would have been massive amounts of people that would have bought rigs. Was it not the best choice for people to buy rigs back in the December/January timeframe? Yes. In my opinion, the time to buy rigs for mining ended back in fall of last year. Most people, no, vast majority of people suck in investments. People suck so badly in investing and trades that they start believing manipulation in the market as the reason why market crashes and bubbles happen.
Panic and emotions rule us, especially in investing. Experience, and that's usually by losing money, allows us to do it better in the future.
That's ok. Because most average folks don't have time and the patience to do proper investing. That's also why only a relative few gain nicely from their investments. Crypto space is no different.