Why corporate bonds rated AAA still have higher interest payments? Isn't it the same as gov AAA bonds? so shouldn't we always just buy corp AAA bonds?

Hi!

AAA rating is given to the bonds of corporates, which have the ability to pay the coupons and repay the invested amount timely. The AAA rated corporate bonds still have a higher interest rate that AAA government bonds because government bonds are considered to be risk-free. AAA corporate bonds can till default if they are unable to repay the amount, but the government can always print more money.
To get the benefits of low risk and higher returns, you can diversify and invest in both so that you get both benefits.

I work at kristal.AI, and it's my passion to evaluate various upcoming investment opportunities.

I think the credit rating only really relevant for off-currency bonds (eg Argentine gov't borrowing in dollars). For local currency, the government can always print more money...

Stepping aside from that for a second - governments still have more strength than even the best corporates - again Argentina saga as example, the government has had much more ability to negotiate/restructure their debts than a corporate would have had.