India lost not because Bumrah was not in the squad. India lost because of their poor batting. The team scored only 185 runs in the first innings. India's batting was even weaker in the second innings. India managed to score only 157 runs in the second innings. India could only give a target of 162 runs. It is very difficult to win against such a small target. So I don't think India could have done very well even with Bumrah in the squad in the second innings. The irregular performance of the batsmen is the main reason for India's defeat.
India had lost the series in one of the worst possible ways and yes, the reason for this loss is the Indian batting. In the first test game, Australia was close but India achieved the victory and celebrated it but it was their first and the last celebration in this series. After that, India played a tour match and won it. They were confident for the next second game in which Australia won it so easily even at the last innings Australia had to make 19 score. In the third game unexpected rain arrived, the match was drawn. In the fourth & fifth game, Australia won both of the matches with huge run rate that resulted in the series win.
Talking about Pakistan, they did worse where South Africa were bowled out for 615 runs while Pakistan lost 6 wickets for 155 runs.
