Initially it was the possibility to make some tiny amount of money in my spear time, nothing more.
Back in the day I was mostly in to faucets, I have accidentally stumbled upon one of those adds filled websites and it just got me interested. Later on I realised what bitcoin is all about, I followed the breadcrumbs to reach the original Satoshi's posts and whitepaper.
Then is became clear, how outstanding and revolutionary the idea was and how important for my own sake.