You may see that President-elect Rohani in Iran had a landslide and yet only won 50.7% of the votes. The explanation is that there were three other candidates.
Getting an absolute majority of the votes in an election with four serious candidates is truly a landslide. The nearest runner-up only achieved 16.5%, followed by a third at 11.3% and a fourth at 6%. See this Associated Press article on the Yahoo News site for details.
Experts were convinced a run-off election between the top two vote-getters was a foregone conclusion. As too often happens, the "experts" were wrong.
