Not only that but as a nation focussed on exports it makes even less sense to cut off trade than as one relying on imports.
These people are racist assholes and their plans are as dumb as they are.
Only if you assume the plan is meant to benefit the country. If you assume that they want to profit from the suffering it makes more sense. Irrational, cult-like mindsets are easier to peddle when people are miserable.
I think they are definitely malicious, but I don’t think they are capable of such cunning planning. They yearn for the Germany of the 50s and 60s and that means, among other things, no EU.