What reasons does gatsby give for daisy original decision to marry tom?

Gatsby wasn't there when Daisy married Tom. If he was there, he probably would've eloped her. Daisy didn't want to marry Tom. That was the reason she got drunk before the wedding.

Gatsby wasn't rich when Daisy was marrying Tom. If he had all the money before her wedding, she would've had no reason to marry Tom.

In my opinion, Daisy married Tom only for his money. She still had feelings for Gatsby!

I didn't actually understand your question, but i hope i answered it! : D