Internal mistake seems to be underplaying it. They do not follow modern SDLC practices, have no mechanism for testing, are unable to rollback effectively etc.

Internal mistake seems to be underplaying it. They do not follow modern SDLC practices, have no mechanism for testing, are unable to rollback effectively etc. The bad software update was a mistake made a global catastrophe due to deliberately bad practices. No tests is not a mistake, they simply did not give a damn.