The reason why Leo decided to do an audition with Harold was simple. A slight fear that the movie won't work at the box office with a lead that was not famous had gripped his heart.
Although many movies have worked at the box office without a famous lead actor, the number of movies which didn't work was much higher. And the difference had just increased in recent times.
Earlier, a movie which would work at a film festival and get good ratings had a chance to do well at the box office with adequate promotions.
But now, studios would release many of them on streaming platforms like Zetflix because the audience prefers to watch them in their homes instead of going to the theatres, this would also help a lot in recovering the budget, and the movie might even break even.