I think it has much more to do with monocropping than with climate change. There are lots of other examples with different crops long before the effects of climate change were noticeable.
This same bacteria causes Pierce's disease in Vitis vinifera, the common grape (from Eurasia). Whereas North American Vitis species are resistant to Xf.
There's a lot of research going into solving Pierce's disease here in the US from breading programs to bacteriophages. The later may end up helping solve the same problem in Olives.