Most likely because it took researchers 2 years to do this the first time. As you can see, this wasn't enough to get them a fair hearing with critics of infectious hypotheses.
OK fair enough, to a point...it took them 2 years to work out everything needed to get the results they got - across a range of 4 tests. But nobody has yet replicated the methods they used in any one of those 4 tests. I think you can perhaps excuse nobody trying to replicate the entire methodology of all 4 tests, but I don't think there's any excuse for a range of researchers running the simple, basic PCR, finding absolutely nothing, and then jumping to publication and saying "there's nothing there to be found, maybe they had a contamination problem".
And part of the WPI's 2 years work was 6 months of rigorous review by Science magazine - the other studies didn't have to do all that.
In my view, they simply disrespected the WPI because they were 'small' and 'not one of us'. They couldn't see past that prejudice, and they can't deny that they failed to find something real and significant as a result. One would hope they would learn from that, but I doubt it very much. They will reconstruct reality to suit their prejudices - and that means saying it was the WPI's fault for not helping them out more in the details of the paper.
I'm afraid that's what they're going to say, and they shouldn't be allowed to get away with it. When they badmouth the WPI, we should ask them: Who made this breakthrough anyway? Not you...
And really, that's what's wound them up the most.