Starting bitcoin mining operation is costly, so I don't think they just do it out of knowledge and belief in bitcoin, everything is done because of money, most especially that those jobs or business that requires highly demanded knowledge comes with higher amount of compensation.
To invest in Bitcoin mining in this day and age, you need substantial capital. No one would invest millions of dollars upfront to start something they have no idea about. Definitely, there is a strong financial motivation that drives them to spend millions upfront.
Bitcoin is known to have an appreciating value, and that goes to say that those who make sure to mine bitcoin are after of the financial rewards that they can get once they start to sell bitcoin, or some would prefer to mine bitcoin so they can accumulate and own bitcoin rather than buying from a centralized market where the price is obviously high.
This argument doesn't entirely make sense. A miner has to invest millions of dollars just to set up a mining farm, whereas it is actually much easier to purchase and hold Bitcoin from exchanges with that same capital. Furthermore, mining machines get updated frequently. If you look at that aspect, the risks of investing in mining are much higher.
