I think you are exaggerating this. Akram and Marshall were better in Aus. Probably others as well.Virtually all ATG fast bowlers who bowled in both India and Australia had better bowling averages in India than Australia. The 2 notable exceptions where Hadlee and Ambrose.
India has been kinder to quicks recently than AUS. But in Kapils time I dont think this was the case.
Just about everyone is better home than away. Its not just about conditions, its about your ability to play in them. Plus your opponents ability to play in them. The absolute best bowlers don't have much of a discrepancy between home/away, because they figure it out. But for bowlers a notch below like Kapil and Anderson, a discrepancy is normal. The difference is less notable when they play in unfavourable home conditions like Kapil, but more so when home conditions are easier like Anderson.
Anderson and Kapil have very similar stats normalising for conditions. Anderson peaked a bit harder and seems to have won on longevity though.