If I am not wrong, most people were able to mine Bitcoin with their CPU back then. I don't know exactly when the mining moved to GPU hardware and then ASICS, but I heard that it was possible to mine Bitcoin through CPU power. How else do you think people mined the blocks? I don't think Satoshi sold any of his mined Bitcoin back then. Some early miners sold their Bitcoin for a very low price.
As another member already said, there were already some exchanges. So, possibly some people also bought Bitcoin at that time. But mostly people acquired their Bitcoin for free. I wish I knew about Bitcoin back then.
True, mining was possible back then but considering the price at the time, it's also easier to just buy Bitcoin, and in 2010 Bitcoin was worth less than a dollar, it was basically worthless. If we had seen it coming, maybe dropping $1,000 on Bitcoin back then wouldn’t have been a big deal. And if we had held onto it until now we’d be living the kind of life most people can only dream of.
As for me, when I first got into crypto, the name I kept hearing was Mt. Gox. Of course, I never got the chance to trade on that exchange since they shut down in early 2014 after people started panicking.