Why is this stalemate?
Black has no legal move. Your idea of moving the pawn is illegal. Black is going in the opposite direction.
Can't move the black pawn because a1, its only possible square, is occupied by the black King, blocking that move.. Can't move the black King because moves to b1 or b1 are into check and a2 is occupied by the black pawn. Thus, no possible black moves. Thus, stalemate.
Isn't our current stalemate result different from an earlier version of chess .... where stalemate was a victory?
Isn't our current stalemate result different from an earlier version of chess .... where stalemate was a victory?
Yes, many centuries ago in the indian and arabian versions stalemate was a win. In the modern form of chess it became a draw (in the 15th century), but amusingly, this was not an uniform rule in Britain until around 1800.
So the point is, no one can remember that time unless they are at least 200 years old.