I think the flow is back on Baku's side now, under the assumption that his original plan involves Leader playing a 'perfect' game (i.e. never dying). Some supporting thoughts:
- His shocked expression when Leader missed his check, followed by his worry that the safe strategy was now gone for him
- Leader died at 8:21 and the next round started at 8:26, i.e. a 5 minutes interval instead of the 2 - 3 minutes he calculated for himself Nevermind, I made a mistake by calculating Leader's starting turn instead of just the interval...
- As we saw in all previous games (esp. Hangman and Air Poker), Baku has to rub an opponent's loss in their faces. Death by injection would likely be too peaceful by his standard
There is always the (obvious) possibility that he's trying to save his old bromance partner, but all things considered (the author's writing style, the prince bee story and other various hints) I highly suspect that Baku considers Leader to be the biggest liar of them all, and has something extra cruel planned for him.