Saturated fat does not clog the arteries: coronary heart disease is a chronic inflammatory condition, the risk of which can be effectively reduced from healthy lifestyle interventions | British Journal of Sports Medicine

Preventing the development of atherosclerosis is important but it is atherothrombosis that is the real killer
The inflammatory processes that contribute to cholesterol deposition within the artery wall and subsequent plaque formation (atherosclerosis), more closely resembles a ‘pimple’ (figure 1). Most cardiac events occur at sites with <70% coronary artery obstruction and these do not generate ischaemia on stress testing.4 When plaques rupture (analogous to a pimple bursting), coronary thrombosis and myocardial infarction can occur within minutes. The limitation of the current plumbing approach (‘unclogging a pipe’) to the management of coronary disease is revealed by a series of randomised controlled trials (RCTs) which prove that stenting significantly obstructive stable lesions fail to prevent myocardial infarction or to reduce mortality.

I would wager the decrease in sugar/refined carb consumption is the most significant factor in the results.