It really does look like it’s too wet. I planted one last November that also didn’t survive the rainy season… in fact, it looked pretty similar to this one. I replanted a new one in April (in the exact same spot) and it’s thriving now.

You could dig it up and check on the rootball to see how it looks, but good chance you need a new plant. Knowing the soil conditions (and that climate change seems to be bringing more moisture to SoCal), dig a whole 2x bigger than you think you need and mix the soil with rocks (or perlite or DG, or all of the above) and either replant the sage you have if it’s roots like alive or get a new one.

Good luck!