HODLing has become popular particularly because of the lack of a need for a detailed understanding of how to trade different assets, and also because of the reduced amount of time that is needed in comparison to actively trading.
No. It became popular because it works while trying to catch a pump or a dump in an unpredictable market, where a company buing coins can cause a 5% pump overnight and Trump shutting down the US borders can cause a 10% dump.
There are a number of problems with HOLDing, however the primary issue is that it is massively inefficient, being that although over a long enough period of time most investments in the crypto space become profitable, throughout that period they could have been a lot more profit generated by actively trading.
You're wrong again. Holding is efficient for those who do not have time to trade. While you feel like you can make more money sitting and watching the price every day and say I made 10 thousand USD trading this month, someone else will go to work and forget about his coins. In the end of the month he'll say I made 10 thousand USD at work, and I also made additional 1000 profit on my held coins without lifting a finger.