It was the most profitable year because it was so easy to gain a thousand percent profit with almost every ICO or altcoin. Now, there are profits, but it is really hard to predict which coin will explode to the moon. Currently, we no longer see such increases on DeFi coins.
Don't forget that, during the 2017 in the eyes of ICO things where good because of their new invention compared to this 2020 with the event of Defi, this two event has actually helped in the beginning to a new era in the cryptocurrency industry. What happened in 2017 has taught us a big lesson that we won't take this 2020. The hype of 2017 did more harm than we thought and investors are just be careful with the 2020 hypes.