Because he was of the same trade (dia to homotechnon einai). Same construction with dia as above. Homotechnon is an old word (homos, technē), though here alone in N.T. Rabbi Judah says: “He that teacheth not his son a trade, doth the same as if he taught him to be a thief.” So it was easy for Paul to find a home with these “tentmakers by trade” (skēnoipoioi tēi technēi). Late word from skēnē and poieō, here only in the N.T. They made portable tents of leather or of cloth of goat’s hair. So Paul lived in this home with this noble man and his wife, all the more congenial if already Christians which they soon became at any rate. They worked as partners in the common trade. Paul worked for his support elsewhere, already in Thessalonica (1Th 2:9; 2Th 3:8) and later at Ephesus with Aquila and Priscilla (Act 18:18, Act 18:26; Act 20:34; 1Co 16:19). They moved again to Rome (Rom 16:3) and were evidently a couple of considerable wealth and generosity. It was a blessing to Paul to find himself with these people. So he “abode” (emenen, imperfect active) with them and “they wrought” (ērgazonto, imperfect middle), happy and busy during week days.