Setién is one of my favourite coaches and I've mentioned him here (and the other forum) quite a number of times. What he done with CD Lugo is practically a miracle to be honest because he not only got them promoted, but then made them a constant feature in Spain's second division and they even flirted with promotion to La Liga a number of times but fading away in the second half of the season.
That bit about his teams fading away toward the end is a constant feature though but maybe it's just coincidence and a lack of funds at those clubs to have a squad strong enough to compete right till the end. Just to say that when he took over Lugo, they were seriously crap!
His name was even mentioned for a while amongst the candidates for the job at Barça with ex Barça director and big time player in every election Tony Freixa who has been very vocal about Quique Setién as the candidate for the job. In a recent interview he said that Setién was already prepared and could give what's needed. But maybe in the future now if he does a good job at Real Betis too. Betis are a massive club in Spain with one of the most fervent fanbases in the country. If he does well, he'll make himself a hero.