This trade mainly just revolves around Giannis wanting out, and Warriors wanting to contend with Steph.
*Note; I am not sure how the picks and salary rules work, but trade machine says it's okay, and teams are so crafty, so they can probably make it work somehow.
BUCKS Reasoning:
Giannis (in this scenario) wants out
Bucks want out of Bobby Portis money
Bucks get 4 first round picks +2 swaps and a few (maybe) interesting young players
Jimmy is still a star that can draw a crowd, even though he is not the same player he once was
GSW Reasoning:
They get Giannis and can contend now
Get rid of Kuminga
Get out of Jimmy Butler's money
THEY GET GIANNIS
Other details:
Andre Jackson Jr. is only in this trade so that the Bucks only need to cut one player, and it doesn't seem like they want him. Overall not that important for the trade.
6 first rounds picks, when the warriors future is still pretty uncertain, might be a little much for them, but if they do win one more championship, then it would be worth it.
Bucks should tank from here on out, and get a top 6-8 pick with their own or Pelicans + GSW first round pick in this draft. Could be a decent start to a rebuild.
Giannis + Steph combo seems really fun
Portis + Draymond seems really fun for different reasons