Trump disclosed his finances as required by law.
His opponents want his tax returns to go on a fishing expedition.
Actually, both he and his opponents both know that his detailed taxes would contain many things that a non-billionaire would not understand, but would also misconstrue as somehow "cheating" or evading taxes.
His opponents would have a field day emphasizing perfectly legitimate practices.
You can bet that some scumbag POS at the IRS would have already leaked anything if it was there.