No, it's trying to prove that Euclid's parallel postulate can be derived from other axioms is what goes back millennia. People were certain it's a) true, b) necessary consequence of other axioms. Gauss was probably the first to consider the possibility that it may be false; others at best tried reductio ad absurdum, arrived to some wildly unusual theorems, decided those were absurd enough to demonstrate the truth of the fifth postulate, and went back to trying to derive it.
It's either true as an axiom or true as derived from other axioms and/or theorems. In neither case does latching onto Euclid's other common notions/postulates/theorems as the selection it must be proved true from make sense as a 1.5kya long task.
I think there must have been a sense that it was true only as an axiom. Proving it from other axioms/theorems was then a goal to secure it's truth "further". But you'd only attempt that if you thought there was something questionable in the first place.
> But you'd only attempt that if you thought there was something questionable in the first place.
No, that's not the only reason. Come on, people actually wrote why they tried to prove it in their commentaries on Euclid's Elements.
For example, some people found that this postulate, compared with the first four, is not really that self-evident and also has a sudden jump in the complexity of its formulation. That's why some courses on geometry replaced it with something different (but equivalent), like "the sum of angles of any triangle is 180 degrees", or "for a line and a point not on it, there is exactly one line parallel to it that passes through that point", or "there are triangles with arbitrary large areas", etc.
