Why do we use Past Simple?
We use past simple to talk about definite past events. There is no connection with the present. The time period is finished. We also use it to talk about past habits.
I wrote ten letters in the morning. It's afternoon and I want to take a break now. (The time period is finished. I can't write any more letters in that time period.)
The plane landed two minutes ago. (The landing of the plane is completed. We know the exact time, which is "two minutes ago".This is a definite past event.)
My grandfather and father played chess once a month (We are talking about a past habit.)