Guardiola does not consider today's EFL Cup match an important match. That's why Guardiola rested key players in the squad today. Champions League and Premier League matches are more important for Guardiola. So in today's match, City played their second tier squad.
However, the overall performance of Tottenham players was quite good in today's match. Tottenham took a 2-1 lead in the first half. Tottenham's players managed to have only 31% of the ball possession in the match. But every attack from Tottenham's players was strong. City's inexperienced players failed to counter the attacks of Tottenham's players.
That's right, also with Guardiola himself he doesn't want to take risks in this match so they rest key players on their bench, this is one of the strategies that is quite good even though they lost by one goal but what the Manchester City players have done is quite good only they lack in defense, also besides that we know their typical game is with ball possession so when their opponent makes a counterattack it is not strange that they are always off guard and this also happens to their main players.
if Guardiola plays their key players maybe the result is a draw or even they can win, but Guardiola has his own strategy which he thinks is the best for their team. Also by playing this second string squad it can be an anticipation for them to be better in the future.