It's the LPS from gram negative bacteria, from the dysbiosis, that causes the leaky gut.
I don't think LPS is a potent leaky gut creating factor. If it was, you might expect that everyone would have leaky gut, as Gram-negative bacteria are very common gut inhabitants. But certainly if there is a large population of Gram-negative bacteria in the gut, then possibly more LPS may be present. I would imagine that to have significant gut leakiness, you would have to be exposed to several factors that promote leaky gut.
I have in the past speculated that LPS in the bloodstream may make it harder for the body to fight off viral infections, since LPS shifts the immune response to Th2. Ref:
1
In my own case, I had the highest level (level 4) of a potentially pathogenic bacteria (Proteus mirabilis) in my gut in my Genova Diagnostics Comprehensive Digestive Stool Analysis 2.0 test; and I also have IBS-D, which is linked to leaky gut.
If we assume that leaky gut allows LPS to enter the bloodstream, then the Th2 shift it produces may possibly have made it more difficult for my immune system to fight off the coxsackievirus B I caught.
However, I have not come across any study which provided evidence that leaky gut leads to the translocation of LPS into the bloodstream. I have seen a few alternative health articles state that leaky gut facilitates LPS translocation, but they don't provide any references for this assertion.
LPS is a large molecule (100,000 Daltons), so perhaps this molecule just cannot pass through even a leaky gut.