racer
The Design points you get is entirely based on how many races you did last season and how far into the current season you are. He only did one race and it was the beginning of the season, so in my eyes the game is doing exactly what it is supposed to (which means everyone who switches leagues will deal with the exact same issue). Whether this is right or not has been debated many times in the forums...
This is the correct answer.
When you joined a new league, your current car design and next season car design was reset.
Your car design for the new season only had one race dedicated towards its development, which is the reason why the car design is not good at all.
You will be able to catch up on design by researching your rivals cars.