It's pretty clear he has most of his money tied up in Tesla and SpaceX. If they go broke, he will be close to broke. It is likely most of the profit from the satellites will go directly into SpaceX to finish developing Starship and Super-Heavy Booster. People on Earth are very likely to need that technology to be working relatively soon. If SpaceX is not able to get them fully functional I suspect it would be a long time before any other company could.
We are not moving with any dispatch to get new generation nuclear reactors developed which are far safer and truly renewable. Virtually all wind and solar power generation plants are all essentially backed up by less efficient natural gas peaker plants which add enough CO2 pollution and worse methane pollution (from leaks) to negate most of their "greenness".
We may well need Starship to set up lunar bases to mass-produce maneuverable solar shades to reduce the amount of solar radiation reaching the earth. Unlike spraying aerosols in the atmosphere, solar shades could be maneuvered or turned off at will if they are causing unexpected side effects. Without Starship, this approach would likely take decades longer, something we may not be able to afford.
If money is available, Starship could also become the critical stepping stone to cleaning up low earth orbit, especially with large and potentially uncontrolled satellites. I know his satellite array has the potential to cause something of a mini-Kessler Syndrome in lowest earth orbits but higher orbits are probably a worse problem because of very long orbital decay times. Loss of access to space could have devastating consequences for our attempts to control climate change.
In the long run, Musk will probably want next-generation nuclear reactors working because he is going to need some form of them to reduce the time it takes to get to Mars and also to produce methane fuel on the surface of Mars during dust storms (which can last for more than a year...).
On the subject of asteroids passing close to the earth, we apparently do not even have space-based telescopes looking for them. If one was discovered on a collision course anytime in the next 5-10 years, Earth would likely have very little to respond with if
SpaceX fails to complete a working Starship system.
Musk has also shown the ability to turn on a dime when convinced of a better approach, this is something that is close to impossible for most aerospace entities. Whatever your personal opinion of Musk, he has a clearly demonstrated ability to successfully make systems work that has been ruled undoable by many experts.
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