Ticketmaster avoided the two-sided market problem until they reached scale. They were just a website where you buy tickets, an IT appliance for promoters.
But then Ticketmaster started buying out promoters, and that short circuited the entire system. Fans can't buy tickets from a different storefront because their favorite artists are only booking performances with ticketmaster-controlled venues. Top talent can't book high-grossing venues that aren't owned by ticketmaster, because Ticketmaster owns the promoters.
Scalpers are a symptom, the disease is consolidation of competitive markets by corporations. This kind of situation is precisely why antitrust law exists.