What was Hungry Joker?
In 2011, Tabata's one-shot Hungry Joker won first place in the Golden Future Cup, the rookie competition that feeds new series into Weekly Shōnen Jump. The serialized version launched on November 12, 2012, and it did not survive the magazine's rankings: it ended on May 13, 2013, at 24 chapters.
Tabata has been candid about why. He considers Hungry Joker a failure with a cause he can name: its protagonist was quiet and dark, the opposite of Tabata himself. Friends who knew him told him the hero should be energetic and happy-go-lucky, the way Tabata actually is. Two years later he opened Black Clover with Asta, a hero with no magic and no volume control, and this time the series ran for eleven years.
The lesson is documented in his own words, and it is the hinge of his career: the cancelled series is not a footnote to Black Clover, it is the draft of it. His earlier career is covered on the Tabata page.