Mauricio Pochettino is not an amateur when comes managing a top club in the English Premier League abd that's why I'm very optimistic that he surely does know why he's allowing many of the first team players at Chelsea to leave.
Pochettino surely has his own tactical style of football and wouldn't want to keep players that he knows would not fit in to his style. Chelsea I believe will do well under Mauricio Pochettino
Pochettino has only coached one English side prior to now, and that is Spurs, and i don't know if Spurs are in the category of a 'top club', they don't wn trophies, neither did they win when Pochettino was manager. Having said that, i am a huge fan of Pochettino's style of football, and that's because he plays an offensive and attracting game, under him Chelsea will definitely play better than they did last season, but i don't think he stands any chance to win a trophy next season.