Why are people living twice as long?

It has nothing to do with burning coal. One could also use wood.
Life expectancy was not in the forties. It was the average lifespan. For every baby who died at birth someone got to be 80.
I am talking about Europe more or less north of the Alps. Other areas of the world it looks different.
People died of illness which today can be healed or helped like tuberculoses, cancer, heartfailure, high bloodpressure the list is about as long as the amount of illnesses.

Firstly, you're facts are wrong. If you check the actual numbers for the 1920s, the average life span (not life expectation) for most odf the modern world was most likely around mid-'50s to age 59 (in USA); other industrialized countries it was around 50 yrs to low-50s.

Secondly, what an odd conclusion that you propose... that breathing coal smoke has anything to do with increasing life expectancy. I've seen not one single reliable resource that makes such a claim. Can you provide a single one that states such a conclusion?

The reason life expectancy increased was due to an improvement in quality of life and economics for the average person, along with less general pollution/better urban sanitation, better nutrition, and better medication and medical expertise.

Jesus says you're full of poop.

With the exception of TB which can be demonstrated, the vital statistics of the ailments you listed are not much different than they were 80 years ago and will continue to be so until scientists take into consideration the deadly results of people's attitudes and life styles.

“What we think, or what we know, or what we believe is, in the end, of little consequence. The only consequence is WHAT WE DO.” John Ruskin (1819 - 1900)

“When we remember we are all mad, the mysteries disappear and life stands explained.” Mark Twain