Hmmm. From my travels through Latin America, I would rate Colombian accents as by far the easiest to understand. Without exception, everyone spoke with clear diction and enunciation. I would definitely not rate it "very hard" - that would be reserved for the Honduran accent, which I found incomprehensible even spoken s-l-o-w-l-y.
Looks like they're rating "difficulty" as "difference from Spanish in Spain". Considering that Spaniards only represent about 10% of the total Spanish-speaking population, I'm not sure that's fair.
A lot of Spanish speaking memes and videos I see have this running joke that Chileans are hard to understand. I don't think it's a literal truth or meant to be taken seriously. They just hand pick a few examples of people who talk very fast, which exist in most Spanish speaking countries (in Spain, Andalusia would be it). There are similar videos in the same circles talking about how hard English is based on a drunk American redneck fisherman or Adele's working class London speech. It's just a meme.
These memes are popular in Latin America, it's definitely not just a Spain thing.
I saw an interesting video showing Argentines in the 90s vs Argentines today, both in BA with more or less the same age and status, and the former group had way more of that "Italian" sounding accent. I think it's going away or softening over time. A shame, because I like it.
Looks like they're rating "difficulty" as "difference from Spanish in Spain". Considering that Spaniards only represent about 10% of the total Spanish-speaking population, I'm not sure that's fair.