First of all, it's about an entrepreneur traveling to the US for a startup, which is directly relevant to a significant proportion of YCombinator founders themselves.
Beyond its direct relevance to the core founding audience of HN, it is not clickbait or wantonly inflammatory, and is clearly of interest to many based on the comment activity and votes.
2) It's too political in nature, and violates the HN guideline that political topics are likely off-topic.
3) It violates the HN guideline that the content should be things that good hackers would find intellectually satisfying. Raging partisan hate at each other about the latest political/social snafu is not intellectually satisfying. It has nothing to do with engineering, science, technology, etc., it's purely a social/political issue.
4) Such a submission only draws a mass amount of hate and partisan flamebait which, once again, does not belong on HN. You have every other site on the internet available to discuss political issues.
5) Your appeal to popularity, saying it has lots of engagement and therefore belongs here, has zero connection to the HN guidelines for what belongs here. I don't care if 1 person or 1 billion people engage with it. It doesn't change the fact that it's off-topic and decreases the quality of the site.