Reading ブラックジャックによろしく manga exercises (p14-and up)

[Zizka]

7: どうしてそのまま死なせてやらなかった

どうしてそのまま死なせてやらなかった

どうして: in what way, in what manner;
まま: once in a while;
死なせて:
Ok, now, I think this is a 〜て form.

@ayamedori

The way I think about it, it has two uses: 1) to connect a verb and auxiliary verbs/grammar points (e.g. , 話し て いる, 試し て みる) and 2) to connect other stuff.

So here it is it used to connect to the grammar point やらなかった, the past negative of やる, “to do”. I think so! If that’s the case I think it just clicked in my head.