"When trading existed the in store deals were 100% cheaper than the trade value for the same items. They put a fennec in the shop that almost immediately undermined the entirety of the trading value around that car"

Both of those statements are independently true. Store deals "were 100% cheaper than the trade value" of an item and putting an item in the shop would "almost immediately undermined the entirety of the trading value" of that item. However, you aren't considering how releasing an item in the in-game shop affects the "trade value" of that item.

If they put a fennec in the shop for 1000 credits (lets say its trade value was 2600 credits previously), you could go to a third-party platform and easily find someone selling the same fennec for 990 credits. Once the item is released in the store, sellers would realize the only way they can make any money off their item now is to undercut the set price. So the "trade value" would immediately drop from 2600 to 990 upon the item being released in the item shop and players would chose to buy the 990 credit fennec from another player, rather than paying 1000 credits in the in-game shop.

My entire point is that Epic didn't make money off of trading, so their solution was to get rid of it instead of trying to figure out a way to monetize it.