Look at the six nations. Simple structure played at the same time every year. Throws at least one good game every weekend. 95 percent of tickets sold and it gets way more coverage than it arguably deserved.
If it moved to a home and away type competition from July to October on say Amazon prime than within two years the majority would forget about it.
29k was decided upon before the outcome of the games were decided. The rental cost is tied to catering etc which they can’t turn around quickly unless they are willing to pay.
The Aviva Stadium needs to be used close to every week to be able to scale up to that degree. Otherwise you have to pay a lot more and have higher ticket prices.