i know this is all theory and conjecture so there's no "right" answer/opinion. so here's my 2cents'...
NO WAY in heck anakin and mace could've defeated sidious, if even THE most powerful jedi of all, yoda, could barely hold his own against sidious. by his own admission, yoda got his ass kicked by sidious.
and as powerful as both anakin and mace were, they're simply weren't in the same league as yoda, let alone sidious. so sidious was definitely playing possum to appear as if he was the victim of jedi ruthlessness.
btw, i absolutely HATED the lightsaber duel between mace and sidious. it was very poorly executed. it was so obvious that neither samuel l. jackson nor ian mcdiarmid were comfortable with the complexities of duelling. so they resorted to close-ups, quick cuts and stunt doubles. what a major disappointment. can't say i blame them though. physical acting and doing your own stunts are always hard, and u need a certain degree of god-given athletic ability to pull it off. ewan and hayden had it in spades though. they always looked very natural in the lightsaber scenes. and of course, ray park's the best of them all! he's da man! :maul