How to gain investors' trust if for security reasons you can't open the information about the project owner to the public?
People will be trusting the developers if these developers are getting doxxed. People will never try to trust any anonymous developers. They may sometime believe in the anon developers just for the gambling purpose and no more. That mostly happened with so many scam tokens.
What organizations are there that provide KYC for project owners?
There are so many platforms that provice KYC for project owner just like pinksale, Certik, hacken and many more. These platforms are providing audit and many features available like KYC verification for the developers.