A year ago at this time, fans were probably wondering whether their nightmare would ever end.After finishing 4-12 and third in the NFC West in 2018, the Niners capped a five-year streak of non-winning seasons Elijah Hughes Jersey , during which San Francisco made the playoffs exactly zero times and played under three different head coaches. The 2011-2013 years brought three straight postseason trips, including an appearance in Super Bowl XLVII, but those were the outlier. Before that, the Niners had mi sed the playoffs in eight straight seasons. In other words, 2018's well-below-average mark was absolutely the norm.How on earth, then, do we explain Kyle Shanahan leading the 49ers not to .500 but far, far beyond it this season? How do we explain San Francisco going from 4-12 not only to 13-3, but then all the way back to the Super Bowl? No matter what happens this Sunday, when the Niners take on the for a shot at a sixth all-time Lombardi Trophy, the team has already made history, becoming just the third team since the NFL existed to win four or fewer games and reach the Super Bowl the following year.Here are five reasons they were able to do it:Super Bowl LIV is just days away, and we've got a gambling preview worthy of the Big Game. Pete Prisco, R.J. White and Will Brinson break down their picks, props, DFS advice and more on the Pick Six Podcast. Listen below and Tony Bradley Jersey for daily NFL goodne s fired into your eardrums.1. Improved offensive lineThis is simultaneously the most underrated part of the Niners' turnaround and the most underrated piece of any title-contending team. Even the smartest football experts get swayed by the visceral thrill of skill positions, throwing all their praise and critique on quarterbacks, receivers and so forth. But it's truly the trenches that make a solid foundation, and San Francisco did not ignore its need for up-front upgrades in 2019, even if those upgrades came via developing depth, in some cases.Joe Staley and the O-line have driven San Francisco's improvement on offense. USATSI Fill-ins and each drew praise in relief of sterling tackles and , while interior starters like have experienced a career rebirth, of sorts. Consistent play along the line has trickled down to pretty much every part of the Niners' offensive succe s.2. A deeper running backfieldThe Niners didn't completely rebuild their running back spot, but the addition of from the gave them a veteran presence for a room that grew in pretty much every way po sible in 2019. Outside of Coleman, couldn't always stay healthy, but when he Dante Exum Jersey had touches, he often made the most of them with surprising big-play burst. , meanwhile, has been a beautiful revelation as an open-field weapon, complete with a historic, breakout performance in the NFC title game.Raheem Mostert is just one piece of the Niners' dynamic backfield. USATSI has obviously been integral to the ground game as well, paving the way for the stable of backs, but it's the depth of the unit that makes it so dangerous. Shanahan has reason to keep going to the RB well because of how smoothly the group works together.3. Picking the Ohio State pa s rusher second overall in the 2019 draft was a smart move for the future, but it also paid off immediately. Bosa may not have logged double-digit sacks in his rookie season, but he might as well have, considering the impact Grayson Allen Jersey he's also had in the playoffs. This is a one-man wrecking crew who's led the Niners' turnaround on the other side of the trenches.Nick Bosa has headlined San Francisco's fiery pa s rush as a Rookie of the Year candidate. USATSI That's not to discredit the rest of San Francisco's rejuvenated D-line, which has been tremendous as a unit. But Bosa is the newest, freshest face outside of Chiefs import , and it's no coincidence the 49ers adopted an increasingly ferocious defensive mindset upon his arrival.4. A fully integrated The former star was active for all but two of San Francisco's games in 2018, so it's not like he wasn't around a year ago, when the Niners were only being talked about as a contender for a top-five pick. In 2019, however, it's as if we saw No. 25 fully integrated into the secondary -- no, the defense.Richard Sherman is playing like a lock-down corner once again. USATSI Both aided by his supporting cast and reigniting his own signature swagger, the 31-year-old reminded his coaches, his teammates and his opponents that you truly can't underestimate the impact of a lock-down cornerback. Sherman's steadine s on the outside has allowed Robert Saleh to play aggre sive and let his guys get after the QB. Georges Niang Jersey And now should give San Francisco confidence entering the Big Game.5. A healthy This is the most obvious one, but it's true nonethele s. Garoppolo has had a penchant for turnovers, particularly interceptions. But there's just no comparison between a Shanahan offense with the guy under center and whatever you want to call 2018, when San Francisco had to rely on and C.J. Beathard.Jimmy Garoppolo has been a calm operator of Kyle Shanahan's offense in his return to the lineup. USATSI Nothing against either of those guys -- especially Mullens, who showed some flair at times -- but Garoppolo is so much more polished, so much more in control. When he's got the O-line working in front of him, he's mostly calm, mostly cool, mostly collected and, thanks to the exceptional a sistance from his ground game and defense, can actually afford to take chances slinging it.