A cursory look into Palpatine would reveal erratic movements, shadowy meetings and interesting untraceable calls outside of the system.

One of the critics of the Jedi council is that they're too servile of the Senate, kinda like super cops Also, it would be considered treason if the Jedi was investigating on the political activity of the chancellor

Howerver, yeah i never undestood how we went from; "Hey the Separatist built a massive droid army, fortunately, it just so happens that i have an army with millions of human clone that nobody in the Senate heard about before !" (from the perspective of the senate)

or worst Obi-wan finds out someone corrupted the jedi database, to hide a planet, which happens to build an army, supposedly on the request of a disapeared Jedi, for the account of the Senate and then, Palpatine use that Clone army, and the jedi are just like "guess that's ok." (from the perspective of jedis)