The leaves are the food factory , without them there can be no growth or tomatoes.
Once the tomatoes are set on the bottom truss that is the time to start using a tomato fertilzer.
The reason for a fertlizer is mainly to boost flower production and tomato growth.
Once three or four trusses are set you can remove some of the lower leaves but not too many as they are making and sending food to the growing tomatoes.
Once the trusses are set sunlight is not so important but warmth is, to encourage ripening.