Martin didn’t start off as a bad person.
He was clumsy and shy, and bad at his job, but he was also caring and kind, in a very simple way. His acts of kindness were plain but sweet in their simplicity, and his demeanor seemed almost childish. I can see how that could make him endearing.
He was quite an uncomplicated character: all that we knew of him was that he’s clumsy, a bit squeamish, fond of insects and other small creatures, and that he wrote bad poetry. A perfect fit into the softie character archetype. You could find him cute, and develop an attachment to him - it was easy since he had no real flaws. But he didn’t have anything unique about him either.