I’d say it’s down to the individual and the leagues they grew up in. South Americans tend to have dirty leagues so they are used to the hustle. Alexis hit the ground running for us.
Also another factor is the position of the players. CAM’s have it easy. They can just float around in space and pop off passes. Wingers have a fullback wanting to kick them 10 feet in their air upon arrival.
Ozil needed no time to climatise at all either.