I think in the ICO stage because they can manage more time to get a better price when they get the target success in their projects and most of the ICO give their time to focus on their project. And I think you can earn a better profit in that situation unlike buying it after the ICO has been finished.
it is indeed the right thought because we can buy tokens at low prices but have the potential to rise high if the project runs smoothly. but in my opinion at the moment it is very risky because there are now many ICOs that end badly.
maybe next year we can use that method if ICO starts to improve. in my opinion now it's better to buy coins that are on the market because the price is down.