Paul had been with Titus in Crete where they had made disciples amongst the Cretans. However, there was work that was yet to be done because the church was not yet in order. It was disorganized and leaderless at that particular point.
Paul had a plan to get it organized, though, which was the same plan that he had at each step in his work. He would leave the church with leaders appointed and intact in each town where they had done their work. In short, Paul did his work by traveling from town to town and doing the work of an apostle, making disciples and leaving them in his wake. Titus would then be tasked with organizing them and putting the leaders in place so that they could continue the work without him.
The reason I left you in Crete was that you might put in order what was left unfinished and appoint elders in every town, as I directed you.
Titus 1:5
This is, in fact, the missional task, that the work should be started, that the Gospel would be proclaimed, and that local leaders should be established so that the work would continue without Paul, or even without Titus following Titus’s work of establishing the leaders.
By doing his work in this way, Paul establishes churches throughout the entire region, through each of the areas where he travels in order that their work would go forward, led by the people locally so that all might hear the word of God through many other workers, not only through Paul and his traveling companions.