What were the breakthroughs behind this?

Over a century of progress in surgery, drugs, prevention, and emergency response has driven down death rates from heart disease and stroke.

For much of history, heart disease was a mystery. Middle-aged adults often collapsed without warning, and doctors usually blamed “dropsy”, “apoplexy”, or simply “old age.”

In 1945 — at just 63 years old — President Franklin D. Roosevelt was sitting for a portrait when he raised a hand to his head and whispered, “I have a terrific pain in the back of my head.” Minutes later, he lost consciousness and died from a massive brain hemorrhage — a consequence of uncontrolled high blood pressure and heart disease, which doctors at the time couldn’t treat.

Cardiovascular mortality rates have declined greatly

Public health efforts and advances in medicine, surgery, and emergency care have all contributed to the decline in cardiovascular deaths

Public health efforts and lifestyle changes have reduced cardiovascular risks

...read more at ourworldindata.org