Some theories and recommendations I spend the night writing.
What if his death was not an incident.
Due to a small interference from a ROB in the killers life that may have lead him,the killer, to desperation to the point where he had to rob to get money.
The being probably slowly manipulating the killers thoughts could make him more desperate to achieve his non-existent goal of over coming debt.
Or the ROB could make him crazy in the moment could have just been like ini-mini-mina-mo catch a f*cker by the toe if he gets that's stab then you know isekai is the way to go.
The protaganist 'Rimuru Tempest' is probably in this world to give spectatorship of his new life to a ROB he has never met.
Making him ourr mc Rimuru make new races, new evolution, introducing Japanese culture and slowly taking away his innocence when he makes the choice to sacrifice ten thousand humans to become a demon lord.
Next time on the half-assed theories will Boruto's Karma hold on to the railing to not get fired with my roast find out next on half as theories.