(Oh dear, I'm not particularly sure if any of us is that much experts on medieval Japanese history. You'll be extremely lucky if you get a proper response.)
Will read on it a bit. Expect an answer in a few minutes.
EDIT: My answer is that the Toyotomi clan was lost once Hideyoshi died. The young Hideyori needs to defeat all the other powerful factions or entice them to alliances, but Tokugawa just needs to defeat Toyotomi. It doesn't really seem either that the battles were neck-to-neck .