[PAR35]

if Calvanism is SO important of a doctrine, why was it not codified clearly in scripture

It is - folks just don't want to see it.

What happened to SOLO SCRIPTURA?

I don't know - it's not a Calvinist/Biblical point. SOLA Scriptura, on the other hand...

[aruanan]

It is - folks just don't want to see it.

Given Calvinism, the correct response would be, "God just didn't want them to see it." Nobody saw it until John Calvin described the "hidden" counsel of God which he said was not explicit in scripture. Like that song says,

The whole world was lost in the darkness of (foreordained) sin
The light of the world is Calvin.

Calvinism: There is no will but God's will and John Calvin is his prophet.