As for this, there are theories such as the story that 'cleaving to the master until the last moment' was accepted by the Bakufu, as well as a penetrating view that it was convenient to say 'the father and son of Sanada were great commanders' in order to cover up the delay of Hidetada, who became the second shogun, for Sekigahara.
これに関しては、「主君に最後まで忠義を尽くす」という筋立てが幕府に容認されたとする説の他に、二代将軍となった秀忠の関ヶ原での遅参を誤摩化すため、「真田親子が名将の方が都合が良かった」とする少々穿った見方なども存在する。