Maybe they prioritized it low, assigned it to a group of 3 devs, and it functioned the first time they demoed it to management, so it shipped. All other devs would’ve been working on their in-house software.
I haven’t heard of a single software job in the last decade that offers anything resembling “training”. You sink or swim based on your previous knowledge, what you can glean from the codebase and coworkers, and how skilled you are at self-teaching.