How do i not win this hand?

i have A10 and opponent has A3 board is A and other cards but no 3 so i have no idea why it would be a split pot??? cost me huge in a 20K buy in tournament

There are many combinations that could have been a split there, what was the exact board?

i had A(spades) 10(hearts), he had A,3 (both clubs)
board ( 8s, Ah, 4s, 9c, 10s)
happened to me here too can u explain?

Your hand K 7
Hand of other player K2
Cards on table K 489 and 10

Your best hand made out of the 7 cards (your 2 hand cards and the 5 on table)
KK89 and 10

Best hand of the other player
KK89 and 10

On this hand yes.

His first hand AsTh vs Ac3c on the 8s, Ah, 4s, 9c, Ts board he should have won. Do you have the replay since it’s impossible to split that?

there could have been a split with say:
8A44J the best hand would have been AA44J, many other examples so please provide the replay maybe you got it wrong.

You both had a pair of Aces and a pair of 10’s, 9 high.