From what I can gather from the translations, its 80% because he finished whatever it was that was part of his apprenticeship in 2 years and 20% because he was acknowledged by 2 big shots MOMENTS after he passed the test (knight captain and head alchemist teacher) with 1 of them being a future member of the hero's party named Veil.
As for the shipping talk, well we've established here that Lucas isn't COMPLETELY at fault (I apologize in advance if I managed to get you mildly irritated). The boy just found someone better and didn't EXACTLY promise OGLaura anything AND Laura was kinda stupid enough not to ask for an answer. Even though it'll look like she would be pressuring him. If anything, the BIGGEST fault I could give him is the fact that when he had the opportunity to visit the village (or at least grandma's hut to ask for her alchemist help), he didn't stop by and let Laura know and reject her right then and there. I forgot if it was mentioned if he was already aware of his feelings for the heroine at that point or if they were in a relationship (then we could at least factor that in) but AT LEAST let the poor girl have the decency to keep her dignity and be rejected because he hasn't thought of her not once on his hero journey (but then again, in-universe its been stated the game wasn't well received because it was cliche and the only reason OGLaura was prominent enough/had a fanbase was because the players thought she was plot important at the first half of the game due to her unique game and exclusive story sprite but the fact that said village visit event didn't mention her at all made the players realize. Ah~ so she wasn't important at all AND was forgotten by the developers too. Poor thing). Honestly though, I do ship her more with Arnold, so far no love rivals on his route too. Plus, if she successfully cures his sister, at least she'll be appreciated more AND they share common interest in alchemy. Lucas still has that vision dreams with Heroine afterall and so far heroine doesn't seem like a bad person as well