Actually we couldn't say that it is pure luck cause everyone knows that profiting in Bitcoin is a serious thing it will need more discipline and self control. Like what other said above those investors buying some bitcoins before when the value is too small and hold it until date then one thing for sure they will partying cause they made a huge profits. But like what I said it's too difficult cause there's a chance that the temptations will almost hit them they almost sell their Bitcoin. But they can manage their self and then now they got a big profits.
Indeed. There is no pure of luck to get profits on Bitcoin. Before people buy Bitcoin, there should a research first about when the right time for buying (entry). People also set a target for their exit time, they don't take profits in a random way. These are serious efforts, it requires good knowledge or skills, too. So, people don't invest in Bitcoin like they are playing gambling. It is untrue that people assume to get profits by the luck. 
Sure, people also need to be patient and discipline in Bitcoin investment. If people can't do these, they may be influenced by the FUDs and fail to get profits. It is not easy to hold Bitcoin, we need to have strong mentality.