It's a bullpen game, which means several arms will be used. Pivetta can't be used today, ditto Jansen, Bello, Crawford, Paxton, and probably Winck. Plus we have now seen Bernardino, Ort, Murphy and Garza--all four of whom have given up runs.
Also, the score is an unsurprising 6-1 because the Rangers lead MLB in runs scored.
My guess, only that, is that going into this game Cora was reluctant to use his best bullpen arms unless/until he could see some scoring from the lineup.