South Africa's pace-bowling talisman had been subdued at times during the tournament but produced his brilliant best when it mattered.
Steyn had Phil Hughes caught at short cover to check Australia's early momentum before returning with a devastating spell of reverse-swing that accounted for half-centurion Aaron Finch, Glenn Maxwell and Brad Haddin.
The 31-year-old's 4-34 was a key factor in South Africa restricting their opponents to 217 for nine - a total that provided few problems for the Proteas who, led by 96 from the in-form Faf du Plessis, knocked off the runs with 55 balls to spare and six wickets in hand.
"I've been looking for some wickets so to get them in a final is always good," Steyn said after being named man-of-the-match.
"Trying to always take wickets, that's the main thing. It's taken a couple of games but I think I've found my length today.
"We were fortunate to get the ball to go a bit through the air too, that always helps.
"If you're always pitching the ball up you've always got a chance of finding the edge or hitting the stumps.
"Today I was lucky, I found that length that I've been searching for."
A sluggish surface in keeping with those served up throughout the tournament persuaded Steyn that full and straight was the way to go - an approach that often makes facing him a thankless task for any batsman.
"Even during the Test match [between South Africa and Zimbabwe] it was very slow," he explained. "We talked about trying to get the ball up and make the guys drive.
"During the one-dayers I went into the form of trying to hold the run-rate back and then today I just decided, you know what, I'm going to go for it and try and get wickets.
"I got the opening batter, Phil Hughes, with a full one and then the rest of them also. I guess that length is always going to be crucial."
Steyn is looking forward to a rare break from the gruelling international schedule but concedes he tends to feel at his best with overs in the legs.
"I've got five weeks' holiday now - I'm feeling beautiful," he added.
"When I'm playing a lot of cricket and I'm playing day after day I get better and better. I think it was proved today."