>Why did they go see the old black guy at that point in time?
>
>Why do they need to go visit the Dude from the Avengers movie
>at the end of Episode 2?

So they are trying to get any information they can on the super soldier serum - Bucky knew that Isaiah Bradley was a super soldier, which means he might have information, they know that Zemo had an agenda against all super soldiers and had a ton of intel on them.