Olive oil contains mainly monounsaturated fat made of oleic acid.
The current evidence suggests that unsaturated fat may be beneficial as replacement for saturated fat, that is by increasing unsaturated/saturated fat ratio. Most of the evidence suggest that polyunsaturated fat may be more benefical for the heart health than monounsaturated fat (Health.gov 2015, Cochrane 2015, Annual Reviews in Nutrition 2016, NMCD 2017).
There is some weak association between olive oil and reduced risk of heart disease, but the included studies could not isolate the effect from other foods consumed:
Researchers in PREDIMED study have found statistically significant association between olive oil consumption and cardiovascular mortality, but when checked for all-cause mortality, the association was no longer statistically significant.
In one meta-analyses, they concluded that olive oil may contribute to benefits of Mediterranean diet, but it's not possible to say if olive oil as such, or only as a source of unsaturated fat, is beneficial (Frontiers in Nutrition 2019). Anyway, a recent systematic review did not bring a clear conclusion about benefits of Mediterranean diet for heart health (Cochrane 2019).
In a recent systematic review, sunflower oil, was associated with lower LDL cholesterol levels than olive oil (Journal of Lipid Research 2018).
In conclusion, currently there is no clear evidence to say that olive oil as such is beneficial for heart, but it could be beneficial as one of the sources of unsaturated fat when replaced for saturated fat.