Complex sentence: On his side, John I of Castile needed Lisbon, not only for financial reasons, but also for political ones: neither he nor Beatrice had been crowned, and without a coronation in the capital he was only a designated king.
Split into simpler sentences: On his side, John I of Castile needed Lisbon, not only for financial reasons, but also for political ones. Neither he or Beatrice had been crowned and without a coronation in the capital; he was only a designated king.