Those aren’t reasons, they are speculation.
They are not speculations.They are reasons.
Just before Paul was baptized and commissioned for his work, the Lord Jesus said to Ananias: “This man [Paul] is a chosen vessel to me to bear my name to the nations as well as to kings and the sons of Israel.” (Acts 9:15; Gal. 2:8, 9) The writing of the book of Hebrews was truly in line with Paul’s commission to bear the name of Jesus to the sons of Israel.
It stands to reason that God would use Paul to write Hebrews. —Obviously if the Bible is a sham, it doesn’t matter. But given the authenticity of the Bible that all scripture is inspired, it is very reasonable to conclude that Paul is the writer.