How are those the same? You need to define "religion" and "sport" rigorously first.

Since you haven't provided one, I'll just use the first sentence on the wiki page:

Religion is a range of social-cultural systems, including designated behaviors and practices, morals, beliefs, worldviews, texts, sanctified places, prophecies, ethics, or organizations, that generally relate humanity to supernatural, transcendental, and spiritual elements.

"Atheism," without being more specific, is simply the absence of a belief in a deity. It does not prescribe any required behaviors, practices, morals, worldviews, texts, sanctity of places or people, ethics, or organizations. The only tenuous angle is "belief," but atheism doesn't require a positive belief in no gods, simply the absence of a belief in any deities. Even if you are talking about strong atheism ("I believe there are no deities"), that belief is by definition not relating humanity to any supernatural, transcendental, or spiritual element. It is no more religious a belief than "avocado tastes bad." If atheism broadly counts as a religion, then your definition of "religion" may as well be "an opinion about anything" and it loses all meaning.

If you want to talk about specific organizations such as The Satanic Temple, then those organizations do prescribe ethics, morals, worldviews, behaviors, and have "sanctified" places. Even though they still are specifically not supernatural, enough other boxes are checked that I would agree TST is a religion.

I have no idea what you're on about with not golfing being a sport.