Here's why:
* Contrast: "Rued" signifies regret or sorrow. This contrasts sharply with the lightness and simplicity of the snowy scene and the speaker's eventual positive outlook. This contrast highlights the power of even small, beautiful moments to change our perspective.
* Subtlety: "Rued" is a relatively formal and literary word, adding a layer of sophistication to the simple description of the snowfall. This subtle formality further emphasizes the shift in the speaker's mood.
* Impact: The word "rued" suggests a change in the speaker's internal state. It implies that something has shifted, that they have moved beyond the initial sadness to a new, more hopeful place.
In conclusion, while "rued" might not be a flashy or dramatic word, its subtle power lies in its ability to create contrast, add sophistication, and hint at a meaningful internal transformation in the speaker.