This is super interesting. I've hear many people make the argument that leagues like the bundesliga or la liga aren't as competitive as the PL but I feel like if that were the case, it would be easier for the top teams in those leagues to accumulate more PPG because there'd be a larger supposed gap in quality from the top teams compared to the others, ergo less competitive league. This graph seems to disconfirm this hypothesis as the PPG of the top teams between the PL, bundesliga, and la liga are fairly similar.

The different number of winners for a league has nothing to do with the variance. I think the person who posted it meant variance among the total points for the winning team of whatever year. Putting an icon of who the winning team was for that year visually just looks nice.