TD hand in the middle of a rush

[Gamblor]

I'm on a rush, I've won 5 of the first 10 pots at a full 6-handed table, many without showdown.

Then this hand comes up:

I have 97654 and open raise on the button.

The BB a bad loose player calls.

I'm not sure he's fully aware of how this game works, but regardless.

I drop the 9 and draw a deuce. I did think about standing pat the whole way and hoping the 9 holds up against an unreasonable but not ridiculous starting hand, but he will stick around for a few draws so I'm goin for the 8, however rough.

Check-bet-call. He drops 2, I stand pat, check-bet-call.

He drops one, I stand pat, check-bet-call.

My jaw drops as he shows A7643 and the chips slide his way.

Apparently I'm playing A-5.