Dante's defeat was the best thing to happen best thing to happen to him and discovering his new malice

looking back Dante's charcters is someone who is ultimately bored with his life and thinks opening up the gates to other will relief from that. He even gave the main cast to prepared which (base on Zenon text you can tell Tabata is selfaware on how he's writing Dante)

Dante at this point in his life has everything.He over threw a king & killed a king and now a leader of a whole country. He's ultimately looking for something or some to entertain him that's why he was eager to face Yami or trigger Asta to use more of his power

As his fight continues with Yami Dante is both hates and loves he has that he has to use more power to face Yami that he's finally getting this thrill he was looking for.

Now let's look at his lost. Asta (w heavy assets from Yami) this no magic, low level devil host manage to scratch him then land the final blow on when he thought he was unstoppable to anyone

Asta who properly has the only power to defeat Dante has became the thing Dante wanted he's new malice. He's even left with the scar as a constant reminder of his defeat. There rematch is gonna be intresting to see

I know some people where disappointed that Dante was the only DT that lost but we wouldn't have this unique character motive if he just beat Asta and left. Yami being taken away acts as more as enough motivation for Asta and the BB to face the DT