"...I don't know anyone who says either a person or group of persons *causes* these books/letters to become inspired..."
People do not CAUSE the writings to BECOME inspired.
If they are inspired ( God breathed, directly from God, etc) then they always were and always will be. It is in their nature. We as fallible human beings sometimes recognize that a work is inspired and sometimes we don't.
The cannon of scripture that is recognized as inspired and included in the Bible was already recognized by the majority of Christians before any council approved. The Council just made official that they agreed upon those works as such. There may be other divinely inspired works, but they will not contradict those that are included in the Bible.
As a Christian grows in Knowledge and discernment the surety of what works in the world are divinely inspired will increase, but one must back check against what is known to be good before accepting something new.
God is just. He will judge our hearts. Seek him in truth and he will guide you.
