"Nucular" is not correct and I don't say it myself, but not everybody has had the chance to learn about the nucleus and nuclear reactions.

Meanwhile, people get along as best they can using the language they already know. And that language includes words such as:

particular
spectacular
funicular
orbicular
and perhaps more,

and these words serve to make "nucular" more natural than "nuclear."

I can't even think of another word anything like "nuclear."