I find such statements inspiring whether they are meant seriously or not, and whether they come true or not.
Elon Musk shows that you can be rich and spend a lot of money without increasing net existential risk. Not increasing it, not decreasing it, just... risk-free behavior.
Space travel does not significantly lower the probability of existential risk because the majority of the probability mass is occupied by human-indifferent superintelligence, which can casually reach into space if it wants to. Also, self-sufficient space colonies are very far off. You need something miles across at a cost of tens of millions of dollars given current technology.
Another point I've made in the past is that as everyone becomes uploads and accelerates their thinking speeds, space will begin to seem very far away. Right now, Luna is 3-4 days away. To beings whose brains are made up of molecular computers with 100 GHz switching speeds, Luna is about 3,000,000,000 days away. That's about eight million years. An eight million year trip to go to an empty wasteland without any art, culture, or much Kolmogorov complexity to speak of beyond geological and mineral patterns?
The near-term future of humanity is to convert the Earth into a "computronium globe" with a web of trillions of simulated worlds within it. In several subjective millennia, we may consume the Moon, but it will be subjective millions of years beyond that until we colonize Mars. In many billions of years, we may be fortunate enough to consume the Sun.