Would

Scientists would discover the disease had probably originated in bats and had then passed through a second species – in all likelihood, but not certainly, pangolins, a type of scaly anteater – before infecting humans."

How did Britain get its response to coronavirus so wrong?
https://www.theguardian.com/world/2020/apr/18/how-did-britain-get-its-response-to-coronavirus-so-wrong

Please explain the use of "would and had ( used twice) in the above.
When do we use the function "–" as used in the above?