It comes down to where their money comes from. Think tanks are funded by people who are looking to manufacture intellectual backing for their political agenda. Given recent developments, I can see a positive aspect to this, because at least it implicitly supports the assumption that research and intellectual arguments matter in politics. However, it shows that you can't conclude anything from the existence of a well-researched and well-argued intellectual support for a position. The think tank system guarantees that anybody with sufficient resources can buy well-researched and well-argued intellectual support.

Which is important. I know I've had a few epiphanies in my time where I realized, "Wait, this thing I thought was stupid, there are some really smart people who are into it... they've invested a lot of effort and research and have some coherent arguments to support it... I should really take another look." It's a meaningful signal in some contexts. In some contexts it even creates a presumption in my mind that I am probably wrong in not recognizing any value in something. In politics, though, it doesn't mean anything, because that kind of intellectual engagement is manufactured through the think tank system as a matter of course.