Startup culture
Startups are traditionally funded by bank loans, crowdfunding, angels or venture capital, all of which require a return on their initial investment. They often start with lofty goals however due to the liquidity of the market and the lack of barriers to entry to a sector competition often erodes non profitable activity.
Startups are controlled entirely by their investors and founders. Even the very first employee is rarely offered more a couple percent equity. That means the mission of the startup is whatever the founders and investors negotiate it to be. The more capital a startup raises, the more it is controlled by investors than by the founders.
All of those dedicated engineers, researchers, scientists, and support staff--the people who signed up to make the technology because they believe in the mission--they don't get a say in how the company is run. If, after 10 years, an oil company wants to buy the startup and never use most of the tech, it will happen. All that IP from that R&D is now gone forever. All those late nights coding were just to make the investors wealthier. A company's mission will always be more flexible than its profit motive.
If you want to start a startup that fixes climate change, don't. Climate change startups are just greenwashed capitalism. If you actually have a mission, then let the structure of your governance match your mission. Start a cooperative, or a nonprofit, or something else--just not a fucking startup. Let the future, dedicated staff that care about your mission actually be stakeholders in your organization.