I replied right away and asked them how they're doing.
What did you ask them about how they were doing?
I asked it knowing beforehand they were going to say
This is entirely fine. In fact, it would be weird if you didn't ask them how they were doing.
Wow, I'm so mad.
Why are you mad? It is the right thing to do to ask others who they are doing. This shows that you care about how their life is going.