The dark side of the force clouded a great deal of their vision and on top of that they weren’t entirely certain of Sidious’s existence till the waning days of the clone wars. Up until the last days of the war Sidious’s existence was speculation for most of the Jedi order.

Makes sense.

City planet and the capital, full of darker emotions clouding the overall view of the world leading to a casual dismissal. They did in fact hint that a lot of it (dark side) surrounded the Chancellor, which is what my assumption for why requiring physical proof of Palpatine’s alter ego became a necessity for the Jedi. They can’t prove guilt to the populace on a feeling lol

Palpatine was so good at hiding his abilities not even Plagueis was aware when they first met.

Could they not have just taken a blood test though

^Palpatine was a beloved Republic senator and later the Chancellor of the Republic. Not to mention he did a very good job portraying himself as a leader fighting for the prosperity of the republic so there wasn’t much reason for the Jedi or the senate to test his blood or question him in general.

Palpatine hid his abilities and his force sensitivity through something called force clouding. Only his most trusted advisers and red guards later royal guards knew of his power. Also with a planet full of corrupt officials and thousands upon thousands of layers of scum and villainy beneath you detecting that would be very hard.

I always found the reasoning and explanation extremely dumb too.