Switch could already run GTA V
Rockstar sees GTA V as a multi-player game mostly, the issue is not related with running it single player but probably a network issue
Also the game has sold 205 million copies. It's clear Rockstar don't need a single more copy sold for this game. They have gave it away for free a couple of times already and it paid itself multiple times and it's a steady source of money
They probably think it's better to use their developers to create new games