Why are there so many snowman themed games? Did you guys think that would win, and make a bunch of assets in advance?
I think people you really wanted that theme to win, and since the choosen theme wasn't restrictive in that sense... why not?
It's both. As Tuba points out, many LDs have a 'sub-theme', in this case '☃', that people occasionally add to their games. However, at the same time, what seems to be an increasing number of people prepares concepts in advance for themes they feel will likely win (despite it being really against the spirit of Ludum Dare), and it's inevitable some of those had no concept for 'entire game on one screen' and went with their idea for '☃' instead.
The most complex when rating games is that many games only focused on the "snowman" theme and not on the "entire game on one screen" : some people have made games with multiple levels, or even scrolling, but with a snowmen.
In the end, I guess the important thing is that everyone made a game, a theme is just a "creative kickstart", not an unbreakable rule.
It used to be an unbreakable rule, actually. From the old competition rules:
3. Games must be based on the theme.
However, it's no longer in the new rules (which are still under development). It's unclear whether this is an oversight or one of the changes making the rules less strict. I really hope it's the former, but it could go either way.
In either case, games not fitting 'entire game on one screen' should definitely get a 1 for 'Theme' regardless of how much snowman it has. The theme was 'Entire game on one screen', not '☃'.
Snowmen arent funny.
Also every single snowman game is a top down shooter with snowballs.
Good implementations of the sub-theme are possible. For example, Tifu's boss rush game has a giant snowman as one of the bosses. That's how sub-themes should be used.