In the context of these experiments the fungi don't really have to do anything in this Mars-like environment, except surviving. Many fungi can do that quite well by going in a dormant state.

If you want to take these results to extrapolate whether there could be living and "thriving" fungi on Mars right now: there are radiotrophic fungi that can extract energy from ionizing (and possibly non-ionizing) radiation. There could also be fungi capable of chemosynthesis, the production of sugar and amino acids using oxidation reactions as a fuel source.