Twitter has never been the largest social network, but it remains one of the most influential — a home to celebrities, journalists, and influencers of all sorts and the go-to network for breaking news. Now, Twitter is trying to expand what its platform can do, offering creators the ability to make money and users the ability to speak to smaller groups and find more relevant content. To do that, it’ll also need to grapple with what seems to have become a perpetual set of challenges: misinformation, harassment, and the company’s own leadership.