Vasser, who has made his name in open-wheel racing, crashed hard into the outside wall when his Dodge Intrepid was clipped in the rear by Todd Bodine's Chevrolet Monte Carlo.
That blocked the track and Jason Keller's Ford Taurus ran into the mayhem. Keller's car burst into flames and the driver was pinned to the inside retaining wall.
Two laps later, Earnhardt drove his Chevrolet under the yellow and checkered flags to score his second straight win in this event and 16th career Busch series victory.
While the celebration was going on in the pit area, Keller was able to climb out of the car that had burned with bright orange flames just a minute earlier, a fitting finish to a race with a handful of scary accidents.
"We're having a great time this week," said Earnhardt, who took the lead from Harvick on lap 55. "I knew the car was good and I'm happy, happy, happy. I can't believe it."
Earnhardt owns the winning car along with his widowed stepmother, Theresa.
"We're both having a good time owning this car," Earnhardt said. "It's a fun series and I'm having a good time today. We still have one more race to go, though. I know the biggest race is ahead and I'll be thinking about it all night tonight. I want to win that Daytona 500."
Earnhardt could become the first driver to win the Budweiser Shootout, a Gatorade Twin 125, the Busch race and the Daytona 500 in the same SpeedWeeks.
Kenseth needed help and did not get it in trying to pass Earnhardt.
"I decided today I wasn't going to take the outside and I was able to get back to second, but Dale Jr. had a real strong car and it would have taken a lot to get by him," Kenseth said.
Harvick led the first 31 laps before the first caution. The yellow flag was for a hard crash into the Turn 2 wall by second-year driver Shandon Vickers. The Hendrick Motorsports driver ricocheted off the wall and ran into the side of series rookie Stanton Barrett. Coy Gibbs and Hermie Sadler were also involved in the crash.
The leaders pitted during the caution, with 38 cars on the lead lap all coming in at the same time. Racing resumed when the green flag waved four laps later, with Harvick once again in front of Earnhardt.
Tennessee's Brad Baker brought out another caution on lap 55 when the engine blew in his Dodge. Harvick pitted for four tires and fuel to help correct a tightening of the chassis on his Monte Carlo. Earnhardt, however, was able to get out in front and was in the lead when the green flag waved followed by Waltrip, McMurray and Mike Bliss.
Harvick's charging system started to fail so he had to shut down the cooling system inside the car in order to save power. But he was able to get up to fourth with 58 laps to go.
Stacy Compton pounded the outside wall in the first turn on to lap 76 with the car erupting in fire. Compton was able to get out of the car safely, coughing smoke out of his lungs. His car broke loose after a right front tire deflated.
The leaders pitted, setting up a situation that could have ended Harvick's bid for victory. He left the pits early, nearly hit Kerry Earnhardt leaving the pits and took off before the gas catch-can man was able to pull the overflow can off the back of the car.
Harvick was penalized and had to restart at the end of the pack in 38th when the green flag waved on lap 81 of the 120-lap race. Earnhardt was back in front and led the pack into the final third of the race. Kenseth was second followed by Johnny Sauter.
Jeff Green had to take over for pole-winning driver Joe Nemechek, who took ill with a stomach virus. Green had to start at the back of the field but was able to move up to mid-pack before crashing in the fourth turn on lap 93.