The thing is that a lot of years people really didn't know much about it. There was this so-called info blockage - mining and cryptos weren't as interesting for media to cover than other news. Thanks to that a lot of people could mine rather well using their GPU rigs and ASICs from first generations.
This lasted up to winter 2017 and then it went into masses as something that is mega easy to do for earning some extra income. And you probably know how it went from there...
Mining does not bring as much profit as before. If you check the statistics, you will see that many miners decided to sell their equipment and started trading. People find that this business can give them more money.