Because my passwords are stored in the cloud but they are only decrypted on my PC. If a nation state or another attacker gets into the password manager I use, they have my encrypted passwords just the same as if they rooted some Linux box I have an account on. The stakes are roughly the same.

A passsword manager (PM) makes random passwords easier. A PM keeps me from re-using passwords. A PM gives me a relatively secure place to store vital information, and it also lets me use it on multiple computers and stays in sync.

Do I trust them implicitly with everything? No. That would be foolish. It's a calculated risk, and the benefits outweigh the risks.