To delete the Steam account, you need to write a message to the technical support, for this go to the official website
Сlick “I need help“, choose the category of the question “My account” and write a message that we want to delete the account.
A week later I received an answer in which I asked if I really want to delete my account.
To which I replied “Yes, I want to delete my account“, after that, about a week later, the second message came:
The Steam account was disabled at your request. All information posted by him in the Community has been deleted. You will no longer be able to sign in to this account or restore access to it.