Bitcoin was something of 2009. There are way better cryptos around now. BTC transaction time is way too slow. BTC transaction fees are way to high. Max transactions per second is 7 which is WAY WAY too slow. BTC has some serious scalability issues. BTC is vulnerable to a 51% attack since the 4 biggest mining pools (which are located in china) control 50% of the hashing power. This means if they and one other mining pool would team up, they could do some serious damage to BTC. Bitcoin has almost no utility. One current utility is being a bridge from Fiat to Alt coins since most alt coins don't have fiat parings. Another utility of BTC right now is using it to buy things on the black market, although this is slowly being replaces by privacy coins like Monero. Bitcoin will also never be a store of value, unlike Gold. Gold has a demand since it is used in electronics and jewelry.. . If your a Bitcoin maximalist, good for you.
Well, bitcoin is not vulnerable to 51% attack if you ask me and if Bitcoin is, we would have experience it before now. However, you're right when you said the mining company team up, they could do some serious damage to bitcoin but I wouldn't do that because it will affect their business cause they'll be the one loosing the most. That's why they won't even pray for it to happen.