They didn't underestimate Botafogo, we can see that from the PSG line-up. They were just unlucky + Botafogo took the tournament too seriously, maybe this is a way for South American players to get on the radar of big clubs, hope they can be recruited to big European teams. It seems that in this FCWC tournament, clubs from Latin have had more good results, if it continues like this it would not be surprising to see the champion of this tournament be one of the teams from there.
An unexpected defeat and maybe this happened because PSG tried to rotate because I saw six players replaced by Luis Enrique. In this tournament it is also not surprising that a number of big teams lost because maybe the coach has a different view in seeing the final opportunities in the competition. But in any case, the defeat should not have happened because PSG itself dominated the game quite a bit and it's just that a number of opportunities could not be utilized properly.
It seems true because we see a number of teams from Latin are more focused and they are more serious about facing the competition in order to achieve victory even though the top teams are also trying to perform optimally by trying to do some rotations for refreshment.