Sensei no Bulge and Hungry Joker didn't have any fandom, they flopped hard. Don't make me laugh.
Putting Black Clover and its questionable quality aside, Assassination Classroom and My Hero Academia made success because they are good series in the first place. If other author made a series as good as them, it would make success the same way. Jump readers who have the trouble to cast a vote do so because they take the magazine seriously and I don't think that they get hyped by names only. The name of the authors means little when the series is shit.
Hungry Joker was very hyped after the GFC. Sensei no Bulge was very hyped as well (If I'm not mistaken, it was the very first "new" series that viz picked for it's shonen jump version). They flopped hard because they were very very bad, not because they did not have fandom (they do even today).
I for instance still think that Hungry Joker is better than Black Clover. Sensei no Bulge was indeed crappy.
And again, I agree, a series will succeed if it's good, independent of whoever is it's mangaka. What I said is... It's EASIER when you already have a fandom, when you already have experience, when you already know how the "system" works. But pay no mind to my opinion.
Just wait for the 3 new rookies relevance against the 3 veteran.
You can quote this message after that =)