Just like every presidential scotus nomination. It's why scotus nominations are so controversial in the first place. If every scotus nominee had loyalty only to the constitution and the rule of law, then whether they are republican or Democrat wouldn't matter.Trump thought that he could put people on the Supreme Court who would be loyal to him rather than the Consitution and the rule of law.
Every president wants to place scotus positions who they think will further their agenda.
For the record, I completely disagree with the whole notion. Anyone who has scotus aspirations should not disclose their political affiliation. If justice is blind, then it shouldn't matter if they lean right or left.