«جَاءَ الطَّالِبُ الَّذِي نَجَحَ»: «الطَّالِبُ» is the nominative subject; «الَّذِي» modifies it and occupies a nominative position; «نَجَحَ» is the ṣilah with an implicit subject-ʿāʾid.
By contrast, in «جَاءَ الَّذِي نَجَحَ», «الَّذِي» itself is the subject. This is an added comparison, not a quotation.
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Relative Nouns — Ṣilah, ʿĀʾid, Forms and Syntax
«جَاءَ الطَّالِبُ الَّذِي نَجَحَ»: «الطَّالِبُ» is the nominative subject; «الَّذِي» modifies it and occupies a nominative position; «نَجَحَ» is the ṣilah with an implicit subject-ʿāʾid.
By contrast, in «جَاءَ الَّذِي نَجَحَ», «الَّذِي» itself is the subject. This is an added comparison, not a quotation.