Explaining research to a non-writer
Every time a feature film set in the past is released, it doesn’t take long for the press to start finding research gaffes from minor stuff like cars on the street before they were made, songs being sung before they were released, and then major problems such as battles being fought in the wrong country and world leaders showing up after they were dead.
It’s hard to explain how such things happen to our readers and viewers. Hollywood, of course, is more of a problem because so many people are involved with each production. Major authors have multiple editors and fact checkers. Small press authors usually have to roll their own research and hope for the best.
When authors write novels, they are primarily concerned with the storyline and the characters. Yet, as one writes, there are dozens of things to check:

Basically, if somebody coughs in your novel and grabs for a bottle of cough medicine, you have to find out whether that cough medicine even existed when the novel was set.
If you were around at the time and place your novel is set, you can’t even rely on your memory. Most people don’t remember nitty gritty specifics. They know they grew up listening to a song on the radio, but do they know what date it was released? Probably not.
When we write our novels, everything is open to question even though we’re writing fiction.