You could believe it is not about money.

Most importantly, this seems to rest more on if you believe the principle was being followed or not.

It is possible to believe one thing, have another person believe another thing, and respect that their decision is sincerely held but subject to a different perspective, as is our own beliefs.

You can stand up for what you believe and still respectfully disagree with someone with a different stance.

The problem is when you decide that reality always conforms to you opinion. If you assume the other person is aware of that reality and decides differently than it becomes a betrayal of principles. Assuming to know the internal state of another's mind to declare that it is for money becomes disrespectfully presumptuous.

Your problem is not in understanding how X can occur if Y. It is assuming that everyone agrees with you on Y.

You might be right about Y, you might be wrong. Even if you are right, it is still possible that Y is a belief a rational person can hold if their perspective has been different,