These individuals telling bitcoin is a bubble are victims of scam through the use of bitcoin. We cannot blame them, because they have experience it. But let us not generalize everything because of the fact that in this industry, there are a lot of scammers especially hackers. So let us be very careful and vigilant as always. Do your own research.
Not all the people who are telling that bitcoin is a bubble are victim of scam, some of them like Warren Buffet is a very wealthy person which became rich because of investing in companies and he is one of the example that keep saying that bitcoin is a bubble because it is a pure speculation since there is no basis for the price of bitcoin but only the emotion of the investor and traders.
Warren buffet is a 90 year old guy (older even?) who doesn't know anything about crypto or bitcoin.