This a good question. Because I made lots of researches about content marketing. For this , I can tell same reasons.

Originality : this is most important thing to be on front side of hot and trend list. Because if you didn't make a original good content , users can flag you.

Quality : quality is about how much information and contribution you give to the user. If the content providing benefits to users, they will upvote the content.

Upvote Bots : Some people don't think the bots is ethical . Because you can directly be in list with giving money to bots . İf you distribute 300-500 steem to some bots , you can be in the trends top.

Reputation score : This plays bigger role on the trend lists. If it is high , it will be easier in the trend list. But we can't say the same things for hot list. Because hot list is not about daily or weekly content. There are new posts in the list .You need to be get interaction quickly after posting the content.

I think that's all. Have fun !