You can make it believable
As a writer you get to make a few assumptions about the environment in which your story happens. Clearly you're not intending to write a futuristic Sci-Fi novel in which humanity has already colonized the galaxy; the question makes it clear that humanity is still earth-bound.
But how earth-bound is humankind's technology? To make the basic story work (single person escaping Earth and settling elsewhere), there must be plenty of accessible resources in the Solar System. And here in 2019, those resources are not yet accessible. They exist - there's plenty of evidence of ice on the moon for instance. They're just not at all useful.
But what we do have in 2019 is robotic space exploration. It turns out robots are the better pioneers, they survive much harder environments. So what if we assume a few decades of slow development towards space mining? Your much-improved AI explains why robots are still preferred over humans in space, and they have a basic off-Earth infrastructure running for basic chemicals such as water, hydrogen, oxygen, steel, etc. 199
Mars can have a robot base with a nuclear reactor in this scenario. But of course, no habitat for humans yet.
No space agencies You didn't exactly say what you meant by "no space agencies". But this is another case where you get to choose what it means, as long as you can make the story believable. So you can just say that the organizations ceased to function as the vast majority of personnel became ill or died, and basic society collapsed so the remaining personnel was no longer funded by the state. But as space mining required a fairly steady pace of launches, this process had been automated to a much larger degree to keep costs down.
Perhaps SpaceX now has rockets that launch and land from underground silo's, where the rockets are resupplied by robots between missions. And without anyone deciding to launch new missions, all rockets have returned to their home silo's and are waiting for orders. Unbelievable? Well, it's the only way in which mining titanium in space could be made profitable, in your story. 199