On Sunday, a mistake in the pits by the Red Bull team handed him a victory in the principality.
Pit stops are always important in Formula One, but that importance is magnified in Monaco's tight confines, where overtaking is so difficult. Despite looking quicker for most of Sunday's race, Red Bull's Daniel Ricciardo was left sitting in his pit box for about 10 seconds, waiting while the team scrambled to find the correct tyres for his car.
The delay allowed Hamilton to jump into the lead, where he stayed for the final 46 laps of the race.
Hamilton's win is a welcome result for anyone hoping for a close fight in the drivers' championship. His team-mate, Nico Rosberg, had a 39-point lead heading into the Monaco race after winning the first four grand prix races of the season. That gap is now down to 24 points (a win is worth 25) after Rosberg finished seventh in Monaco.
Rosberg's winning streak, which included the final three races of 2015, ended with Max Verstappen's surprise victory earlier in May at the Spanish Grand Prix. Mercedes have not gone two races in a row without a win since the Hungarian and Belgian Grand Prix races back in the summer of 2014, but it nearly happened in Monaco.
Instead, Hamilton drove a perfect race in tricky wet-to-dry conditions, taking advantage of Red Bull's error and the tight confines of the Monte Carlo streets to steal his first win of the season.
In a televised interview after the race, Dieter Zetsche, chairman of Mercedes parent company Daimler AG, told Sky Sports' Ted Kravitz the win was important for Hamilton's confidence and to even out the "imbalance" in the team.
That was a reference to the mechanical issues Hamilton has suffered throughout the season, including during Monaco qualifying. Those problems cost him a chance at victory in China and Russia and led to wild claims of a conspiracy in favour of Rosberg.
On Sunday, it was Rosberg's turn to suffer—this time with a brake problem.
Ricciardo started on pole after a brilliant qualifying lap, with Rosberg and Hamilton behind him. The first seven laps were run behind the safety car as the track slowly dried. By Lap 15, Rosberg was 13 seconds behind the Red Bull and clearly holding Hamilton back. The team asked him to let Hamilton through and he obliged.
When Ricciardo pitted on Lap 23 to switch from wet tyres to intermediate, Hamilton stayed out, allowing him to take the lead. As the track continued to dry, the intermediate tyres were clearly faster, but Ricciardo could not find a way past Hamilton.
Finally, Hamilton pitted for slick tyres on Lap 31, with Ricciardo staying out for an extra lap. The Aussie should have rejoined back in the lead, but his team did not have the correct supersoft tyres ready for him.
"Basically there was a miscommunication as to what tyres were in the garage at what time," team principal Christian Horner explained after the race, per Autosport's Ben Anderson and Matt Beer.
"There was a scramble, with the mechanics originally having the soft tyre ready."
Ricciardo's assessment on the podium was more laconic: "Two weekends in a row I've been screwed now."
The quote referenced a lead he held in Spain before an extra pit stop put him behind Verstappen and the two Ferraris.
For Hamilton, though, Red Bull's mistake may be just what he needs to turn his season around. And as heartbreaking as the race was for Ricciardo, it is hard to argue Hamilton did not deserve to win. On a day when so many drivers got it wrong, ending the race planted in the Armco barriers, Hamilton executed a difficult strategy perfectly and held off a determined Ricciardo.
Last year, Hamilton was ecstatic to qualify on pole, but an ill-timed pit stop cost him the race. This year was the exact opposite: disappointment in qualifying and ecstasy in the race.
On Saturday in the post-qualifying press conference, after qualifying behind Ricciardo and Rosberg, Hamilton said, "I don't really expect too much from tomorrow. I'm going in with the goal, of course, of trying to overtake the two cars in front—but we shall see."
We did see.
And while drivers are understandably loath to gloat over the misfortune of a team-mate, Hamilton will no doubt take some private satisfaction from Rosberg facing some of the adversity he had experienced so far this year (evening out the imbalance Zetsche referred to).
On the other hand, despite winning the race, Mercedes cannot be completely satisfied with the result. Rosberg's brake issues show that the team are still struggling to find the reliability that impressed everyone so much in the preseason.
Luckily for Mercedes, Ferrari have not had the pace to challenge them regularly, but Red Bull are steadily improving.
Hamilton's win signals a renewed battle in the drivers' championship, but could Red Bull or Ferrari also take the fight to Mercedes in the constructors'?
The Canadian Grand Prix is next, which places much more emphasis on engine power (Mercedes' greatest strength) than Monaco did.
"If we can be quick in a couple of weeks, then I think we can be quick really for the remainder of the season," Ricciardo said in the post-race press conference. "If we can fight for a podium in Canada then we should be able to fight everywhere else."
After seven long months without a win, though, Hamilton will not be worried about Red Bull and Ferrari—not right now.
For now, he is back where he belongs, in the middle of the championship fight.
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