LeBron James was named Finals MVP and was immense for the champions in the last game as he scored a triple-double which included 28 points, 14 rebounds and 10 assists.
The Lakers dedicated the victory in remembrance of Kobe Bryant, who led the team to their last title in 2010, and died in a helicopter crash in January.
Anthony Davis, who came to Los Angeles after years of frustration in New Orleans, was mentored by Bryant at the London Olympics and said he was proud the Lakers did not let down one of the game's greatest players.
"He was a big brother to all of us. We did this for him," the 27-year-old said amid cheers from his team-mates.
Rajon Rondo exploded off the bench with 19 points with the same amount coming from Davis, whose greatest contributions came on the defensive side of the ball.
Davis had 15 rebounds while Kentavious Caldwell-Pope netted a vital 17 points for the Lakers.
Miami never recovered from a slow start despite Goran Dragic checking in for the first time since injuring his left foot in game one.
Bam Adebayo top-scored for Miami with 25 points as well as 10 rebounds, but it was Jimmy Butler's quiet night that gave the clearest indication of Los Angeles' dominance: he had kept the Heat in the series previously but was limited to just 12 points courtesy of heavy defensive pressure.
The title was Los Angeles' 17th and James's fourth following stints with the Heat and his hometown Cleveland Cavaliers.
He became the first player in history to win the Finals MVP with three different franchises, which will lead to further debate about whether he or Michael Jordan is the greater player.
James would not entertain that discussion as he accepted the Larry O'Brien championship trophy, saying simply that his team had earned the respect of fans and rivals before adding: "And I want my damn respect too."
Twenty-two teams had entered Disney World in Florida to conclude the pandemic-interrupted 2019-2020 season, with the isolation zone referred to as the "NBA Bubble" eventually used by teams to promote the Black Lives Matter movement.