Currently on the coinmarketcap site only about 1590 projects compared to at times more than 1700 projects. They have left many projects without developers or scam projects. I personally invested in some of these projects and lost a lot of money like bitconect and centra. Do you trust the projects you are investing in and will keep them for a long time until they succeed or are they just looking for profit in the short term?
I think not all failed projects were created as scams. Some of these have a real platform and a legit team. But the current bearish market has affected the sale of these projects and failed in their ICOs. The team had no choice but to stop the project. Some refunds their investors but some, because of anonymity, have decided to just run away completely.