Sentences

Hello, I have questions in the following sentences. If you answer my questions, I thank you for answering.

Q1.

Perhaps Harry Potter and the Deathly Hallows, and the earlier six volumes were genuinely brilliant-despite the fact that eight publishers declined to publish the first volume. But although success is at least partly determined by intrinsic quality, it is also possible that what people come to like depends very much on what they believe others like. In such a world, the explanation for why a particular book becomes a hit may be as simple as this publisher’s: “It sold well because lots of people bought it.”

Q1. In the above passage, can I paraphrase ‘what they believe others like’ into ‘popular popularity’ or popularity among people?

Are both[‘popular popularity’ or popularity among people] correct?

Is Popular popularity somewhat clumsy?

Q2

Salespeople who are optimistic sell more than those who are pessimistic by 56 percent.

Salespeople who are optimistic sell 56 percent more than those who are pessimistic.

In the above sentences, is the sentence below grammatically correct?

Please reply.