How many human organizations have come and gone on the face of the planet? They pop up and disappear. Maybe they last for a year. Maybe even centuries. All kinds of helps are put into place so that the means and aims of the organization will live on. Officers might be elected, documents written, rules passed, collections taken, battles fought, membership rallies held, pamphlets printed (or posted), but the organizations pass or change into something else. The luckier ones are studied in history books.
So Christ wished to have his teaching and life carry on. How does one make this fullness of revelation foretold by the prophets last for two millennia so far? Mere human institutions fail. So He established a Church under the direction of the Holy Spirit. (And really, it must be a Divinely inspired institution or else how could it survive us?) He taught His disciples and charged them to teach what He gave them. The disciples handed on what they learned to others, in particular to men we call bishops. They in turn hand on what they have received, teachings, examples, prayer, institutions that exist or develop under the Holy Spirit, and continue to do so to this day – one generation after another passing on the faith under the guidance of the Holy Spirit. Thus does Scripture and Tradition come to us, reflecting God’s image to us, not only informing us and keeping us on track, but keeping each other in line also, Scripture informing Sacred Tradition and Tradition making sure the proper interpretation of Scripture is handed from one century to the next.