Richard Hillman was very like Steven (property scams involving Audrey and others, a string of murders and deceitful behaviour to all and sundry) but his story was done so much better. For one thing, it was woven into the narrative, whereas Stephen pops up every fourth episode or so, does a dastardly deed then disappears again. For another, the whole thing was over in months. Gail met Richard, viewers began to realise he was a wrong 'un as she fell more deeply in love with him, he bumped off a few victims, married Gail, attacked Emily and murdered Maxine then was caught all within a relatively short timeframe. The 'romance' side of things was a slow burn, but from his first murder to getting caught only took a year or so. Stephen seems to have been hanging about drugging, scamming and murdering people since the dawn of time.
Craigie was a mere twinkle in his daddy's eye when Hillman was around, too
. If he'd been available, 'Norman Bates with a briefcase' would have been bang to rights immediately.