Neither. They basically see Rust as the future. They want to be able to attract young contributors and to hire young employees who are excited about Rust and who want the safety features. Bear in mind, the average age of the Linux developer is increasing. They also see technical benefits in Rust. And they are increasing test coverage of both the Rust tools and the tools written in C, IIRC.
In reality, I think it much more about taking more control over parts of the ecosystem - the license change is part of it, but also getting rid of the old stubborn communities and maintainers.
There is a reason all FOSS OS alternatives for embedded systems like Zephyr, NuttX, FreeRTOS, IDF, Arduino,... are not GPL based, while Google has purged Android and ChromeOS from it, with the Linux kernel being the only GPL piece left.
I was only thinking about the software, yes. Also a lot of the "Arduino" libraries are not really owned by Arduino, even if they like to attach themself to it, so while it is true what they write about different licenses of the libraries, this what not what I considered to be part of Arduino itself. I was only thinking of the buildtools they release. While these are board specific, these are often "just" a fork of gcc, board-specific linker/image builders, a flasher and the Arduino-build system. Only the latter is what they actually created (arguable not even that: https://arduinohistory.github.io/).
