Complex sentence: To produce them would require the application of a magnetic field stronger than what a superconducting condensate can sustain, so a type-I superconductor goes to non-superconducting states rather than forming vortices.
Split into simpler sentences: To produce them would require the application of a magnetic field stronger than what a superconducting condensate can sustain. Thus a type-I superconductor goes to non-superconducting states rather than forming vortices.