TonusOH...who is Paul?
An enjoyable but impenetrable mystery. It has been suggested that Simon Magnus and Paul (Saul) are divergent traditions about a single man. The names are actually cognates and there are many parallels. Half of early Christians hailed the miracle working Simon as origin of their Christianity, these are also connected to the group that preserved the Pauline epistles. Marcion learned from a Simonian named Cerdo that the epistles by then in circulation had been Judaized, heavily redacted and interpolated. Marcion himself may not have even known of Hebrews as he neither includes or rejects it in his canon. It's all very provocative but too much is lost to be sure of anything.
Language in Hebrews is found verbatim in 1 Clement suggesting the same author reusing his arguments. Problem is we don't know which came first. And the language they share is being utilized differently, in fact opposingly. 1 Clement is impossible to date as internal evidence is contradictory. The work had many recognized additions and interpolations. We don't even know who Clement was and traditions about him are contradictory and come through a procession of hearsay. A Clement is mentioned in the Shepard of Hermas as someone of importance but the work is very different from 1 Clement.
In the end my best guess is that , no one knows.