The best won and they didn’t get a free ride. Here’s why:
People who attended the previous Worldcon and bought memberships for the 2017 and 2018 Worldcons got to nominate works for the awards. So best novel received 2078 ballots cast for 652 nominees, and to become a finalist an author needed just 156 votes (a person can nominate up to 5 works in a category, but in that case each nomination is worth just 1/5 as opposed to a single nomination which counts as a full vote). You can see that nobody is barring members from nominating any work they liked. Members of Worldcon 75 then got to vote on the finalists, with 3319 fans casting their ballots.
For Worldcon 75 they used a new transferable vote system, which makes it impossible for organized blocs of voters to achieve a victory unless lots of other people also supported their nominated works. This was in direct response to the Sad/Rabid Puppies exploiting the voting mechanics in 2015 and 2016 to punch above their weight. The puppies were essentially organizing like a political party, nominating a slate of works that were more or less in line with their views. Then they told puppies to vote for that slate, rather than according to their individual tastes. The new voting system is designed to hinder blocs of voters from hijacking the awards, ensuring works can win on their merits.
Here you can see how transferable voting worked at Worldcon 75:
Note that most of the Hugo finalists were female so hardly surprising they did so well this year.