I am not sure if you're right to say it's good for the industry. Seeing the number of scam ICO I don't think it is helping the industry at any point (other than giving a bad reputation). 0nly 44 % of the projects were still active 120 days following the end of their fundraising campaign It may be good for companies/projects trying to raise funds as an alternative to the traditional ways, however, entrepreneurs are now going back to the old school methods.
Also, a study by PwC found that out of a dataset of ~3500 ICOs, “only 30 % of those have closed successfully” or “lost momentum.”
See the decline


People usually sell theirs token immediatly after the token sales ended and as soon the token is listed on a exchange. It usually create a dump in the price. The one not selling their tokens so soon are the ones really believing in the project. However, most of the investors don't really care about the project directly, they're more interested in the profits that can be made