Although the engineering aspects are likely to garner the most attention, followed by the ethical motivations of existential risk mitigation and exploration virtue, I found the event's economic and business framing to be the most compelling part. If you have the time, it's worth watching the event in full (starts at t=22m):
In general, space stuff is dominated by a small group of intensely committed fans, mostly drawn from math, science and engineering backgrounds. Although an increasing number of space enthusiasts are arriving via philosophical justifications about existential risk and species resilience, the field is still mostly focused on the technical aspects of rocket design.
That certainly makes sense: there are hard scientific and technical hurdles that must be overcome to truly achieve sustainable space living. Hardcore space geeks, whether technical or philosophical, play a crucially important role in keeping the momentum going. Musk explicitly described how space progress had stagnated prior to SpaceX filling the void, a feat made possible only because of Musk's ethical fanaticism. He expressed wariness over personal participation in space travel, for fear that his death would result in a corrupted SpaceX in hock to profit-maximizing investors.
So clearly the intensity and idealism associated with space progress is a necessary and special part of maintaining our current trajectory.
But the overarching theme to Musk's talk wasn't about engineering or philosophy. It was about economics and business.
Musk understands that to overcome the engineering challenges and accomplish ethical goals, you need resources--lots of them. This means talking about business logic: consumer demand, cost of production, price elasticity, investment and payoff schedules, diverse revenue streams, access to talent, integration with government infrastructure, etc.
These aspects of space often get lost in popular media coverage, in part because of the strongly idealistic and inaccessible cultural norms of most space people. To really take off, space companies need to attract and incorporate stakeholders who are totally uninterested in all the geeky intellectual shit. Market forces largely allocate resources and shift incentives, and so they both constrain the development of space economies and enable them.
Musk is helping to reintroduce space as merely another high-tech growth industry, as opposed to a geeky futurist curiosity. Paradoxically, by stressing the practical business realities of space colonization, he makes the enterprise seem more realistic, grounded and achievable while also revealing how frustratingly slow, incremental and difficult it will be.