They did work collaboratively towards a standard. They just also in parallel worked on their own project, because they know standards can take an indefinite amount of time, so it could have been a decade to get USB C fleshed out, while they had already been working on Lightning in the background.
Apple has been a member of the USB-IF (the group that creates USB specs) since at least 2009. https://www.loopinsight.com/2009/07/24/palm-reports-apple-to-the-usb-implementers-forum/
https://www.engadget.com/2009-07-24-palm-complains-about-apple-to-usb-governing-body-while-pre-it.html
https://www.macrumors.com/2009/07/24/palm-reports-apple-to-usb-compliance-organization-over-itunes-syncing-issues/
Really my point was just that Apple designed the lightning connector instead of working collaboratively toward a USBc-like standard
They did work collaboratively towards a standard. They just also in parallel worked on their own project, because they know standards can take an indefinite amount of time, so it could have been a decade to get USB C fleshed out, while they had already been working on Lightning in the background.