The one change they did make is promoting Mattingly to Offensive Coordinator (which, I'm not 100% sure, but sounds like he would be the hitting coaches' boss).
I'm torn on Martinez because he's been here for a lot of positives (one of the top offenses in baseball from 2020-2022, Vladdy's big breakout, the emergence of Teoscar, Gurriel, Jansen, Semien, etc.) so there's some track record of success with him.
Mattingly joined as a bench coach with the expectation that he would help the offense. The team immediately took a step back. They promoted him to Offensive Coordinator and have since taken an even bigger step back. Everything he was brought in for has gotten worse since he got here. Hell, there was talk about helping Vladdy get better at first and even that's moved in the wrong direction.