B"H
Dear Rabbi Gopin,
Thank you for the question. Might the answer be as simple as that the Torah is not always written in chronological order?
The bigger point is that we can find here an answer to our question from the Parsha several weeks ago in which they died: "Were Nadav & Aviyu considered good or bad people?" - "They died because they drew too close to G-d" shows us that they were good people, desiring the closeness of Hashem, although they chose a mistaken path to express it. This may be the lesson of their death for our lives. We should choose Hashem's path and not our own interpretation of it.
Mordechai Selsky
This parsha begins with a warning to Aaron not to enter the Holy of
the Holies. In order to reinforce the warning, the parsha begins with
the death of Aaron's two kids, because they died because they drew to
close G-d. If the death of Aaron's children is quoted to reinforce
the warning to Aaron, why wasn't it mentioned right after the event
happened? Why wait three parshas?