Monaco Grand Prix turned out to be a totally different race in terms of strategy. It is well known that street circuits like Monaco are less harsh on tyres and it was expected that most drivers will opt for a two-stop strategy while few will gamble on one requiring a single stop.
However, one stop strategy became the default strategy due to various reasons. First of all, teams expected rain at around lap 28, thus they focused on trying to extending their first stint. Had they pitted during early 20s, they would have had to make another stop for wet tyres. However, the rain never happened, atleast during the race, The second reason was that many drivers like Vettel who started on soft(prime) tyres made a long first stint and were posting quicker times on used primes than others on new primes. Vettel made the most of his strategy and did a long 46 laps stint on prime tyres. After he made his stop, he joined the top-runners train in 4th place. He need not make another stop, had the rest made another stop, Vettel would have won the race, so other drivers focused on saving tyres and thus made only one stop.
Vettel's tyre strategy
Sebastian Vettel put on a brilliant strategy to finish in 4th place after starting from a lowly 9th place. He decided not to run in Q3 meaning he could start from whichever tyres he want, and he chose the soft(prime) tyre. He jumped three places at the start and was leading the race from lap 31 as other front runner, who started on option tyres made their pit stop. Despite being on older tyres, he managed them beautifully and pitted only on lap 46. During this period, he once increased his lead to over 17 seconds, before Webber and the rest of the field started to respond. He needed a lead of atleast 21 seconds to come out without losing a place. However, He came out ahead of Hamilton in 4th place after his stop. Had the rain occurred, he would have easily went on to win the race.
Paul Di Resta was another driver who brilliantly used Vettel's strategy. After a below average performance is qualiying which made him start the race in 14th place, Di Resta started the race on prime tyres, did a 35 lap stint on it followed by a very long 43 lap stint on option tyres to finish the race in 7th place ahead of his team-mate Nico Hulkenberg.