Hello Lisa,
I share your point of view about Grand Duke Michael Alexandrovich and found him one of the few members of the Imperial Family that really could have made a difference. However, I think Kerensky was not the only one to underestimate Michael's personality.
Princess Olga Paley wrote "We all knew him to be lacking in character and under the malign influence of his wife, Madame Brassova..." and "After a few minutes' hesitation this characterless prince gave in, to the great joy of those traitors to their country..."
Olga Alexandrovna's memoirs: "Misha was Nicky's only remaining brother. He could have given Nicky so much help. I tell you again that all of us were to blame".
Probably pro-monarchists saw Michael somewhat responsible for the downfall of the dynasty when maybe he never had the chance to be of much help, since due to his constant unapproved affairs or marriage prospects (Dina, Princess Beatrice and then Natalia) he was kept not very close to his brother.
I hope my message makes sense in English.
Regards,
Alex M.