Credit and blame are two faces of the same coin, and both aren't worth as much as you think.
When I was young, I was very concerned with credit and blame. My old mentor, Thor Johnson, called me "a shameless self-promoter," and he meant it as a compliment.
When things went right, I made sure I was positioned to take credit. When things went wrong, I made sure that someone else got the blame (I had to be pretty subtle about that!).
Yet now that I'm older, I realize that focusing on credit and blame is a waste of energy, especially in the startup world.
Credit only matters when there's a success for which to take credit.
Blame only matters in big organizations, where you're trying to avoid getting fired by a pointy-haired boss after some disaster.
Both are a second-order concern, orders of magnitude less important than making sure your startup is actually successful.
When an entrepreneur comes to me and tries to take credit for success, I just smile and remind him or her of Winston Wolf's line from "Pulp Fiction": 'Let's not go sucking each others' d--ks just yet.' There will be plenty of time for that after the company sells.
When an entrepreneur comes to me and tries to blame external circumstances, I'm not interested. I only care about figuring out the causes of failure in order to avoid it in the future, assuming there is a future.
In other words, credit AND blame are both a waste of time.