Can't speak from inside knowledge, but it has been observed when this was asked in past that during slow period (middle of night, U.S. time; Sunday mornings) it takes surprisingly little activity to rise quickly to top (if only briefly).
This makes sense, really. So few votes are cast (on page #1 of the newest, often seemingly 10-per-50-posts) that people voting means something is significant.
May be, but it lets luck play a bigger role and looks like an abusable feature.
It's a feature that means that those of us living outside the continental USA are not disadvantaged.