They just want to hand our technological/scientific leadership position over to China. This is ironically, a sort of Cultural Revolution that the Trumpists are espousing - they're suspicious of anything they can't understand and would prefer that PhDs go out and earn their living doing hard labor in the fields and tshirt factories. This is essentially Maoist ideological purity. Our economy is going to suffer, but it won't be felt right away so most of the rubes won't understand and will instead blame our problems on foreigners and immigrants like they always do.