I could write it up, but this article explains it more. You should really be learning Gochisousama Deshita (ごちそうさまでした) too.
I feel the article is flat because normally you learn both expressions at the same time because it completes a small ritual to, literally thank the cook.
I’m not sure how true this is but a Japanese friend said Gochisousama Deshita means something slightly different along the lines of “thank you for your lives” and you’re saying that to the food as well as the chef.
ご馳走 (gochisou) means feast. 様 (sama) is a highly honorific suffix. でした (deshita) it was.
Basically literally saying "that was a great feast", as it is said after eating the meal and leaving the establishment. Not sure why the Japanese friend would say that.
If you look at ご馳走 it quite literally doesn't mean feast. It refers to the people/effort required to rush deliver all of the fresh ingredients to prepare the meal. It's a consequence of Japanese aversion to starting things directly.
You don't say "it was a great feast". You say "it must have been a great effort mustering the horses and men for this"
Of course the expression is used commonly enough that the de facto meaning is basically that now.
https://cotoacademy.com/itadakimasu-and-gochisousamadesu/
I could write it up, but this article explains it more. You should really be learning Gochisousama Deshita (ごちそうさまでした) too.
I feel the article is flat because normally you learn both expressions at the same time because it completes a small ritual to, literally thank the cook.
Also em dash galore.