There could be several reasons why Steam is not opening. First, you need to check if Steam is down or there are any issues with their servers. You can check Steam's official website or Twitter account for any updates on server status.
If the servers are fine, then try restarting your computer and running Steam again. If that doesn't work, try checking for any updates for Steam or your computer's operating system and ensure that you have the latest version installed.
Another reason could be corrupted files or folders in the Steam installation directory. You can try verifying your game files in Steam by going to Library > right-click on the game > Properties > Local files > Verify integrity of game files.
If none of the mentioned solutions resolve the issue, you can try reinstalling Steam after backing up your game saves and preferences. This should fix any corrupted files or configurations that may be causing the problem.