For example, most electricity grids are still partially carbon-intensive, despite renewable sources being cheap and available and in use. Simply buying some more solar panels and hooking them to a carbon-intensive grid will displace coal or gas emissions by the following lunchtime, far more cost-effectively than any form of carbon capture.
I understand the principle on working on research projects that have a long lead time. But Stripe should treat carbon capture as such, and could have a more cost-efficient climate strategy: put most of this money today into the most cost-efficient solutions available today, rather than putting its entire budget into the least cost-efficient solution.