1) I was new(er) to the forums and I wanted to share in and take part in a community event. I didn't really have any expectation of winning, nor did I really have any idea if it would be something I'd enjoy (I can be a bit of a wet blanket), but it turned out to be quite fun.
2) I think so. I'm not much of a physical collector when it comes to games and definitely not one when it comes to VNs, so digital suits me just fine. I'm interested in World End Economica, so it's nice to have two different games to aim for.
3) I'd say longer contests are more fulfilling and fun, but they do require more out of both contenstants and judges. Physical prizes do give something tangible to chase after and I can see how they'd be more desirable, but digital prizes are often cheaper and you have a wider range of options to give as a prize.