Businesses should definitely support the open source projects that they use. I'm still astounded that professional developers seem so adverse to paying for the tools and libraries that they use to make their own money.
Is it so hard to imagine that they do it because the PSF's work is important and they want to support them? All the AI labs depend hugely on the Python ecosystem and infrastructure. Startups burning cash spend on many things that are important to them.
They are heavily focused on code. Claude Code likely generates 100 of millions lines of Python a day, make the language a little bit better with $1.5M is extremely high leverage.
And if this money improves PyPI security (part of the focus), that reduces the chance of Claude Code adding malicious packages to a code base (a well publicized case of this could be a big PR headache for Anthropic). This donation is likely much better leverage than trying to somehow add mitigation at the Claude Code level.
The donation is earmarked for security concerns, ie. improving PyPI from a security perspective to prevent/mitigate supply chain attacks, etc. This means a more healthy Python ecosystem, which also benefits their products which are utilizing said ecosystem likely more than any other.