Here you go:
1. Geopolitical influence. The Western world, lead by the USA, wants to dictate terms of trade in the Pacific before China can. This means laying the groundwork for the environments that western businesses and investors are comfortable with. US investors would be less likely to invest in Malaysia if Malaysia was instead following China's lead on IP protections.
2. Stabilizing of third world countries. By providing the frameworks mentioned above, third world countries take a few steps towards providing open and inclusive economies, and the benefits of the trade deal ensure that their leaders are less likely to take steps that would sow uncertainty in their own economies. Also countries with trade agreements are far less likely to go to war with each other. This was one of the main benefits of NAFTA with Mexico too.
3. Straight growth benefits. Every country is predicted to get some additional GDP growth, though large and already liberalised countries like the US won't see too much. On the other hand, poorer countries like Vietnam are predicted to get a staggering 11% extra GDP growth. That's amazing, and will lead to vastly reduced poverty in SE Asia.
4. It includes a glorious fuck you to tobacco companies. Seriously, it blocks them from using ISDS at all, and it sent so many lobbyists into a fit when it was released.