Why did the lender get offended when I ask them if they can match the rate?

I already have a preferred lender and a pre-approval before finding my real estate agent. Then, when I was about to submit an offer, my agent asked me to compare my rate with their recommended lender.

I called and they asked me to forward my lender’s quoted rates. They did indeed give me a better rate based on an estimated 780 credit score and asked me to submit an application. After I submitted my application, they pulled my credit and it shows 770. So, I emailed and asked if it would affect the quoted rates. Waited one day and no reply.

It was only when my offer got rejected did that say “yes, your rate will be increase by half a point”. Not only that but they submitted approval to the seller on my behalf (not sure if that’s allowed?).

After the offer got rejected, I went back to my previous lender and they quoted me a better rate with my credit score. So, I’ve decided to go with my lender but I wanted to give the agent’s lender one more chance because they recommended them.

I asked them if they can match the rate and they got really mad, saying that’s not how they do business and don’t want to work with us on this transaction.

What did I do wrong?