Q-A: Why are there so many denominations?

1 Tim.1:15-16 This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief. 16 Howbeit for this cause I obtained mercy, that in me first Jesus Christ might shew forth all longsuffering, for a pattern to them which should hereafter believe on him to life everlasting. 

...of whom I am chief...

Paul committed the unforgivable sin by blaspheming the Holy Spirit. He committed this sin as a Pharisee when he watched Stephen being stoned to death by his approval. This event of killing Stephen triggered the beginning of the end for the Jewish program of law. From this point onwards, God would start the transition to the Gentiles.

...for this cause I obtained mercy...

Since Paul could not be saved under the Jewish program of law anymore, the only hope for him was to be saved under another program. But there was no other program yet in existence! It was at this point that God would activate the next part of His great plan of redemption; the program of grace towards the Gentiles (without the use of Israel). For Paul, this was a display of the great mercy of God who would yet save him under a new program even though he was doomed under the law. No wonder Paul would write that he was the chief of (or foremost of) sinners.

... in me first...

The key word here is 'FIRST'. First in what? —Salvation of course! But how could this be since God had shown mercy to save many others before Paul? Paul was certainly not the first person to ever be saved! No, but we must understand that Paul's conversion started a brand new 'mystery' program, the program of grace, and he was the first to be saved into this new program. Paul is the first member immersed into the Body of Christ. He was divinely selected by the risen Christ to become the apostle to the Gentiles (Acts 9:15; Gal.1:1). Christ would reveal to him the secrets of this new dispensation (Eph.3:1-5) and provide him the gospel of grace (Gal.1:11-12). This is why Paul says that in Christ Jesus he has begotten us through the gospel (1 Cor.4:15).

...Jesus Christ might shew forth all longsuffering, for a pattern...

The pattern mentioned in this part of the verse means that all who follow Paul, all who come to salvation my means of his gospel of grace will be a pattern of the salvation that Paul experienced, which is pure grace alone, without any added works* or efforts. Besides the pattern of salvation by grace alone that Jesus showed through His longsuffering, it could also imply that Paul set a pattern that the Church, the body of Christ should follow, through his knowledge of the mysteries (Eph.3:4) and his lifestyle (1 Cor.4:16; 1 Cor.11:1).
*See Faith and Works during the Law Program for details.

Conclusion

There is a reason why so many schisms exist in the Church today, why there are so many different denominations, why there are so many different interpretations of biblical content, traditions, and ordinances. The reason is because people either reject Paul and his message, believing it to a fraud, or they do not understand his unique apostleship and doctrine, or they have not taken the time to study the Word and deduce the myriad of evidence it reveals to support Paul's office. The verdict is out; Paul is the founder of the Church, the body of Christ, its first member, and why all Church doctrine for today (under grace) is found only in the letters of Paul. If you have not come to this conclusion before, then use today as the starting point for studying the Word rightly divided as per instruction of Paul in 2 Tim.2:15.