Well, if you are truly wondering, I think I can give you some intuition about "why they were so pissed". Obviously, I don't know what were the facts of the situ

Well, if you are truly wondering, I think I can give you some intuition about "why they were so pissed". Obviously, I don't know what were the facts of the situation, and if they really should've been pissed, but I can explain the typical mindset. The main idea is that writing some code to achieve any particular effect in the system is typically easy. But writing code, that is efficient and maintainable isn't easy. So, there's a team X, which has people working on some specific system. They own the code. To them, their work isn't quite about "implementing requested features". It is about inventing proper abstractions that both reflect the logic of the requested feature and reasonably anticipate the logic of any future feature requests. They want to avoid having 2 implementations of the same thing, they want every piece of code to be idiomatic to their system, etc. And they are right thinking like that, BTW. Every new developer they get is treated with some suspicion at first, and when he learns the idioms of the system he becomes a honored member of the team X. If he fails to learn them, he gets fired or passed to another team, where he may turn out a better fit. So, for the members of team X, they are professionals, who know how to work on the product and on the system X. Members of other back-end teams are probably not, even if they are good devs otherwise. Some frontend dev — doubly so. Some junior frontend dev coming from military or helpdesk or whatever — triply so. So, you may think that you are a great and charitable developer, who just implemented a Feature. But to them, you are a lowly ape who made a wobbly hut out of some sticks and leaves that is going to fall down now any moment, and it's going to fall down on THEIR heads (and you will be long gone). Worse than that, they understand, that other non-engineers (like their manager) also are prone to mistaking a wobbly hut for a Feature. And you basically humiliated them in front of these people by "solving" their problems (while in fact you created more problems). So it gets political here. In fact, because of that, even if the above is not a fair description of your work, they kind want it to be fair, they want you to fuck up, because it at least makes it easier to explain why your help wasn't a real help. And, in all fairness, it is kinda unlikely that a guy who is new to a codebase didn't fuck up in any way, even ever so slightly. Especially if that's a kind of guy who doesn't understand why dedicated back-end and front-end teams exist.