Alternative construction of ときている


I was reviewing my Anki N1 cards when I saw this
[sentence](https://japanesetest4you.com/flashcard/learn-
jlpt-n1-grammar-%E3%81%A8%E3%81%8D%E3%81%A6%E3%81%84%E3%82%8B-to-kite-iru/)

> 観察が鋭くて頭脳の働きが早いときているので、情報を集めてくる手先としては理想的だった。 (His quick observation and
> active brain made him an ideal agent for gaining information.)

Based on [this](https://japanese.stackexchange.com/q/24096/29327), ときている shows
emphasis. Does this mean that からこそ can be used instead, without causing a big
difference in nuance?

> 観察が鋭くて頭脳の働きが早いからこそ、情報を集めてくる手先としては理想的だった。




They are not interchangeable. からこそ emphasizes a cause-effect relationship
("exactly because of", "this is the very reason"), whereas ときている by itself
emphasizes some unexpected fact ("on top of that", "what's more", "you know
what", "behold" or simply "!!"). I don't know why all the examples of きている in
that page are followed by から/ので, but that's not a requirement.




They are not interchangeable. からこそ emphasizes a cause-effect relationship
("exactly because of", "this is the very reason"), whereas ときている by itself
emphasizes some unexpected fact ("on top of that", "what's more", "you know
what", "behold" or simply "!!"). I don't know why all the examples of きている in
that page are followed by から/ので, but that's not a requirement.

