Hello,
I recommend that you disconnect from the internet on all of your devices.
Then, you will want to use a different device to sign into your accounts and start the recovery process on your accounts. You may have to wait 30 days on Microsoft accounts to change sign-in info, depending on how the hacker(s) changed your information.
After you've recovered all of your accounts, consider turning two-factor authentication on, using apps like Microsoft Authenticator or Google Authenticator. This way, you will need two steps to log into an account, and it will be harder for hackers to get into your accounts. In addition, make sure to change all passwords on your accounts.
It may also be a good idea to start the process of resetting your devices after you've recovered all your accounts so that you can have a clean start.
As for your question about why it's super easy to take control over accounts, it may be because you've installed some sort of virus on your PC that either logged your keystrokes and took the passwords you were typing, or a virus that sends passwords remotely to a hacker. It's a good idea to not reuse passwords across devices and use non-browser password managers like Bitwarden, 1Password, or Proton Pass (there are many others) so that you don't have to remember your passwords. I say this because Google Password Manager stores passwords in your Google account. However, if a hacker gains access to your account, they now have access to all of your passwords with one click. This contrasts with Bitwarden or 1Password because they use master passwords that only you know.
I hope this information helps, and if you have any questions, please do not hesitate to ask!