Submission title is misleading (and not the article title). Fungi did not survive in space outside the ISS, but in a pressurized environment designed to be similar to the surface of Mars.
Then, there was some scientific curiosity about how certain life forms, such as complex plants or insects, might adopt to near-zero gravity. This was a bit harder to justify in practical terms, but interesting and hard to replicate by other means.
But what's the objective with this test? We can easily recreate similar conditions (pressure, temperature, illumination) here on Earth. So what have we learned to justify the cost? I'm not trolling, it's a sincere question.
: In 2018, Mars Express located a large lake of liquid water under the Martian polar ice.
https://web.archive.org/web/20210902121223/https://earthsky....
: There is a chance that this dusty and dark ice might melt a few centimeters down. And any subsurface liquid water produced from melting will be protected from evaporating in Mars’ wispy atmosphere by the overlying blanket of ice.
Is it likely that Fungi would end up in the right places on Mars, and even then grow in these conditions? Probably not. But worth investigating given what is known of psychrophilic fungi.
https://link.springer.com/article/10.1007/s11157-016-9395-9
: Fungi are able to grow and survive at low temperature and exist widely in polar and non-polar habitats. These cold regions are known for very low temperature, high ultra violet-B radiation, frequent freeze and thaw cycles and low water and nutrient availability.
The main user of oxygen is the mitochondria, and even some non-anaerobic fungi can survive fine after losing their mitochondria.