Why did Harriet Beecher Stowe write a novel instead of publishing newspaper articles?

Harriet Beecher Stowe did write newspaper articles in addition to novels. "Uncle Tom's Cabin" was serialized in the National Era, an abolitionist newspaper, in 40 weekly installments from June 5, 1851, to April 1, 1852, before it was published in book form in March 1852.