I think for some who did use bots it was just a way for them to mess with the contest and enjoyed it while others did it and thought maybe Anker wouldn't enforce the rules.
They could increase security by using a captcha (the thing where you prove you're a human not a robot). The problem with making stronger voting regulations to prevent it is that it'll keep your friends/family/followers from voting for you since it's too difficult. It might not gain as much traction, and as a result Anker would get less exposure and advertisement. Hopefully they're other options too that can secure the future contests while still making it easy to vote.