helterskelter
G.O.A.T.
Why smaller countries? Roddick, Fish were super motivated in 2004 also. Chile isn't that small of a country when they pounced for two golds. Argentina isn't small, and we saw Del Potro play his heart out.
Thiem is from Austria, he couldn't care less about the medal.
This is simply a personal thing IMO. Rosset had already brought gold home, so Federer wasn't going to do something unique in that aspect. Sure Federer wanted to do it, but I stress again, as he pointed out himself that the Olympics have a very special place in his heart because of meeting Mirka.
You may well be right that people differ according to personal preference rather than the size of their country. Still, it could be for Federer personally that he wanted to win it for Switzerland even though Rosset had also won it for Switzerland. That is a plausible personal preference even if he hadn't met Mirka at the Olympics. He seemed also very invested in winning the Davis Cup for Switzerland, so he might be quite patriotic. I can imagine meeting his future wife would also be a fond memory, especially as he was only 19 at the time of the Sydney Olympics.
BTW, I think Mainad was thinking not so much of the literal size/population of the country but of the frequency with which they win medals. Chile doesn't often win that many golds. Argentina has been very successful in football, but it hadn't had as much recent tennis success and I'm not sure it's that successful in the Olympics in general. True that many American players have tended to be quite motivated by the Olympics despite the USA winning lots of medals.