Actually, I am not sure about Greece, but in Russia, yes, Christianity appropriated many old Pagan traditions.

so there is a feast during which people eat buttery crepes, play games, greet the spring, do natiobal martial arts, etc.

The feast lasts for a week. So people who start Lent are well fed and a little tired from all that butter and dough.

the first week of Lent introduces mild restrictions. I am not certain, but if I remember correctly, no meat. People can still eat delicious fish dishes, and, in fact, monks over the centuries developed fish recipes specifically for Lent.

then, gradually, week by week, it gets stricter and stricter. Animal fats for cooking are forbidden. I don't remember when alcohol gets forbidden. Then fish, etc, and the very last week before Easter is the strictest. And then people feast on Easter. So basically Lent is a time between two feasts and is a multi-stage process of giving something up.