Also, "GPU on demand" sounds _a_lot_ easier than "drone-based delivery". Between Seti@Home/Folding@Home/etc, various grid-computing/clustering/orchestration stacks that already exist, etc it seems reasonably doable to implement in a year or so. "drone-based delivery" sounds capital-intensive, sounds like you'll need to spend a lot of time building a professional network of business people who might use the service (so there's a 'cultural friction' between techie founders and business folks, potentially), plus the ever-looming threat of Amazon/etc figuring this out first.
tl;dr: I agree it's weird pivot, and good on the founders for being able to make the change! :)