One way would be to sign deals reserving venue space in advance for a good chunk of the year. Artists wanting to perform there on dates reserved to Ticketmaster would need to sign exclusivity deals.
This has a network effect. The more they do, the more effective is the strategy and the easier it gets to keep doing it.
By dangling more money.
In the 1980s, Ticketmaster beat the competitors (e.g. Ticketron) by offering the venues a better financial deal.
Ticketron charged the venues a service fee. Venues pay Ticketron.
Ticketmaster flipped that around and made a clever proposal: instead of charging the venue, we'll charge the concertgoing fans extra service fee(s) and we'll give the venue a percentage of the fees collected. To sweeten the deal, we'll even pay the venue _upfront_ money as part of signing an exclusive deal.
https://thehustle.co/the-sneaky-economics-of-ticketmaster/
That's why most ideas about creating a new ticketing startup to "disrupt Ticketmaster" are naive about how the underlying business deals actually work. E.g. if the well-meaning programmers have idealistic motivations to create a new "fair ticketing" system that doesn't charge outrageous fees, the venues will not sign up with you which means you have no tickets to sell at the "cheaper & fair price".
Why would the venues use your new "fair ticketing" system if it means they get less money?!? That's the financial puzzle a viable Ticketmaster competitor has to solve.
What I find strange is that people aren't usually reluctant to sign exclusivity agreements because it's very limiting. How did ticketmaster get so big to begin with to force / convince people of signing exclusivity clauses?