For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness,

Here it says men suppress the truth. The truth of what? The knowledge about God.

because that which is known about God is evident within them;

This knowledge they have about God, Paul says, is evident within them. But how?

for God made it evident to them.

This is how. God Himself made this knowledge about Him evident to them. You mean God did? How?

For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen,

Through His creation, they themselves, everyone and anyone calling themselves an atheist has clearly seen His attributes, His power, His nature.

being understood through what has been made, so that they are without excuse. — Romans 1:18-20

They understand through creation. They just suppress the truth in unrighteousness. In reality they have no excuse. There are no real atheists. None have ever existed.