This is a false dichotomy and betrays a lack of understanding of the actual work of the scientific community here. The mortality of the fungus and amphibian behavior are both affected by climactic conditions. It is far from “easy” to attribute the epidemic to global warming but careful studies are illustrating how different temperature envelopes and humidity can cause this fungus to thrive in amphibian populations. I suggest you take a few minutes to read this study, it might change your perspective.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1685858/