If I invest in a popular project does that make my money safe from scams or popular projects can turn to scam as well?
What popular project are you referring to? Is it a project that has been listed on the stock exchange, or is it still in the development stage. Popular is not a guarantee of scam or trust, but popular brings one step more success than unpopular. For example, Terra is a popular project, but we can see what Terra has been up to so far. That is, popular is not a guarantee of a trust.
but at least with luna it still have some value even though the crash is so bad that it affect the entire cryptocurrency market, if it had happened to some unpopular coin they'd vanished into thin air, meanwhile with luna it still retaining some value and become shitcoins instead and still famous till this date, I think that's the difference with popular and unpopular coin.