--> Nothing wrong that coworkers want to perform and every boss wants to see it - you can get used to it and be more competitive. Next time, you will reply the email to everyone that you will take care of it if you believe you are the right person to handle it.
同意你的所有comments, 但是，具體這件TASK分兩個連起來的部分，第一部分是我做的，如果你不知道這個部分，不知道整個PICTURE,你是沒有辦法做第二部分的。問題是，這個同事想當然的自己做了第二部分，結果完全是錯的。
--> The resaons behind it could be various which could be totally out of your control and your boss doesn't have to explain everything to you. Your boss has his power to make it the way you wanted but he might have his concerns or his ways to handle things. Or, maybe, at least, he was happy about the fact that someone stepped up to help even though it didn't work out well.
從我的了解來看，你最後的一個情況，就是這裏的情況。
聽起來，你有做BOSS的經驗。Please take a look at my anwers in my other follow-ups.
Thanks for sharing.
