Having started a small avalanche, what does one do with an undefended cutting stone?
9 looks like a severe mistake to me. White may simply capture the single stone and be satisfied, like this:

$$B Simple punishment
$$ ........-
$$ ....Ob..-
$$ ....XO..-
$$ ..1.XO..-
$$ ...XOX2.-
$$ ...cOa..-
$$ ........-
$$ ---------


After this, if black c, white may answer at a, or may tenuki. Tenuki is reasonable, because the black followup does not threaten white, only captures two stones and ends in gote.

(If W2 instead at a, which is sometimes a good move, then black has a cut at b. This cut is worth more than the black descend at c.)

In other words, the cut at b works a lot worse than in the joseki for black. At the same time, black is not strong (e.g. the point you played at in the game remains a weakness). Territory is white's, too. This is not an even result.

As for why B1 was played at all: It is indeed a shape point, because it makes black a work (to capture the two white stones). In some other joseki that look (vaguely) similar, it is actually the correct move.

The underlying reason why the order was wrong becomes visible if we compare with the joseki move. If black plays at W2 instead of B1, then it is significantly harder to capture him in the corner (four liberties instead of two). That is why, in the joseki, white will need to offer a trade, losing two stones but capturing the stone at B1. (There is a ladder involved etc., but those are details.)