Why does setting `umask` to `0077` (and then downloading public key) makes a gpg public key unavailable for apt?

Why does setting umask to 0077 makes a gpg public key unavailable for apt when installing a package, e.g .

umask 0077
curl -fsSLo /usr/share/keyrings/brave-browser-beta-archive-keyring.gpg https://brave-browser-apt-beta.s3.brave.com/brave-browser-beta-archive-keyring.gpg 
  echo "deb [signed-by=/usr/share/keyrings/brave-browser-beta-archive-keyring.gpg] https://brave-browser-apt-beta.s3.brave.com/  stable main">/etc/apt/sources.list.d/brave-browser-beta.list
apt update
apt install brave-browser-beta

The above does not work, I get this output:

Err:4 https://brave-browser-apt-beta.s3.brave.com  stable InRelease    
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0B31DBA06A8A26F9
Reading package lists... Done
W: GPG error: https://brave-browser-apt-beta.s3.brave.com  stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 0B31DBA06A8A26F9
E: The repository 'https://brave-browser-apt-beta.s3.brave.com  stable InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

This does work:

umask 0022
curl -fsSLo /usr/share/keyrings/brave-browser-beta-archive-keyring.gpg https://brave-browser-apt-beta.s3.brave.com/brave-browser-beta-archive-keyring.gpg 
  echo "deb [signed-by=/usr/share/keyrings/brave-browser-beta-archive-keyring.gpg] https://brave-browser-apt-beta.s3.brave.com/  stable main">/etc/apt/sources.list.d/brave-browser-beta.list
apt update
apt install brave-browser-beta

Why does setting umask to 0077 (and then downloading public key) makes a gpg public key unavailable for apt? The key was downloaded as root, and so was executed apt update, why then this issue?