Grand Theft Auto games have always been about running around for a while, causing chaos, playing online, and then take a break.
that's actually a complete and obvious lie as there was no official multiplayer for gta games until gta 4 came along.
it's funny how you mentioned "causing chaos" as 1 of the activities you can do in the game after you beat it.
that's funny because this is also a lie you can't do sh*t. everyone already know how you get wanted level after you kill some random ped in the middle of nowhere, but there're far more game killing features than this. like:
how you can't run over cars with Dumper or Rhino since the cars immediately blow up and they blow you up too,
how there''s no cheat code to replenish your character/car health whatsoever
how JB 700 weapons don't work outside the mission (this car would be such a killa to just dive it around and they ruined the opportunity)
how fragile your characters are, a few cops can take them down in less than 5 secs i think, and even the military bulletproof vest can't help it
and the list goes on. i could bash the game for a few ours more, but the bottom line is - you can't cause chaos and all that there's to do after you completed the game is to take a break.