Did people need the gospel in that place? Of course. Was Paul doing what God had called him to do on his missionary journey? Apparently so. Did he have a working strategy for reaching new regions? Sure. He had a good track record. Were there others willing to go along and support ministry in Bithynia? Sounds like it.
But Paul turned aside to go elsewhere. Macedonia wasn't his chosen destination, even though it turned out to be a great place to plant churches. His own ideas fell by the wayside. His career / ministry goals were swept aside because God had other things in mind.
We don't read that Paul stewed over the change of plans. There was no hanging around and pining for what could have been. We don't even read that other people did the work he had hoped to do. Bithynia was "over" before it began. Instead, Paul and coworkers immediately set their feet on deck of a ship, sailed in a new direction, and evangelized southern Europe.
If you're wondering why your planning is coming to nothing and you can't get a handle on the future, consider Acts 16. Maybe your ship is about to dock at the harbor - and Macedonia is a stormy ride over an open sea, just where God wants you!
Great story of his own journey to Macedonia by our friend Earl Creps: Defenseless http://believedoubtseek.org/all-saints/p
*The Rock, his work is perfect, for all his ways are justice. A God of faithfulness and without iniquity, just and upright is he. Deuteronomy 32:4 NLT
*I wait for the LORD, my soul waits, and in his word I put my hope.My soul waits for the Lord more than watchmen wait for the morning, more than watchmen wait for the morning. O Israel, put your hope in the LORD, for with the LORD is unfailing love and with him is full redemption. He himself will redeem Israel from all their sins. Psalm 130:5-8 NIV
*[Paul] also came to Derbe and to Lystra. A disciple named Timothy was there, the son of a Jewish woman who was a believer, but whose father was a Greek. The brothers in Lystra and Iconium spoke well of him. Paul wanted Timothy to accompany him, and he took him and circumcised him because of the Jews who were in those places, for they all knew that his father was Greek.
As they went through the towns, they passed on the decrees that had been decided on by the apostles and elders in Jerusalem for the Gentile believers to obey. So the churches were being strengthened in the faith and were increasing in number every day.
They went through the region of Phrygia and Galatia, having been prevented by the Holy Spirit from speaking the message in the province of Asia. When they came to Mysia, they attempted to go into Bithynia, but the Spirit of Jesus did not allow them to do this, so they passed through Mysia and went down to Troas.
A vision appeared to Paul during the night: A Macedonian man was standing there urging him, “Come over to Macedonia and help us!” After Paul saw the vision, we attempted immediately to go over to Macedonia, concluding that God had called us to proclaim the good news to them. Acts 16:1-10 NET