The reason is very simple and documented on mother meta: question views do not count towards the arbitrary hotness points formula that is used to determine whether a question is ‘worthy’ of making the HNQ list.
The only metrics that influence HNQ are:
- question score
- answer count
- cumulative answer scores
- question age in hours
The formula is documented on mother meta, but with MathJax enabled here, we can make it look much nicer:
$$\begin{align}\text{hotness} &= \frac{\lfloor n(\mathrm A), 10\rfloor \times s(\mathrm Q) \times 0.2 + s(\mathrm A)}{\lceil a(\mathrm Q) + 1, 6 \rceil^{1.4}}\\[1em]
n&:\text{number of}\\
s&:\text{score}\\
a&:\text{age given in multiples of 1 hour}\\
\mathrm Q&:\text{question}\\
\mathrm A&:\text{answer}\end{align}$$
The numerator increases linearly with the score of the answers and a higher question score as well as a higher number of answers will also make it increase. When ten answers have been added, no additional answers affect the hotness points any more.
The denominator is a weighting fraction that increases once the question age hits $\pu{6h}$.
Further weighting factors are added. One of these is a traffic consideration factor to help smaller sites appear in the list. The other is a multiple question decourager that will penalise each additional question from the same site by a certain factor. Aside from these two mentioned in the post of mother meta, it is unknown whether additional weighting factors are added.
To conclude: The question already had three answers with a question score of 1, meaning the first expression of the numerator was $0.6$. The cumulative answer score would be added to that. Since the question had not degraded past six hours, the denominator was still at its lowest possible value. This probably gave the question just enough edge to make it onto the list.