What is the difference between the sentence in bold and "only Egyptians were skilled enough to navigate and colonize the Pacific"?

[Goooodman]

This text is from TOEFL.
For example, British anthropologists G. Elliot Smith and W. J. Perry assumed that only Egyptians would have been skilled enough to navigate and colonize the Pacific.
What is the difference between the sentence in bold and "only Egyptians were skilled enough to navigate and colonize the Pacific"?

 

[grassy]

The first one is less certain than the second one.

 

[Uncle Jack]

Did the Egyptians navigate and colonize the Pacific? If they did, then "were skilled enough" is fine, but if they did not, then the sentence is hypothetical, and "would have been skilled enough" is far better.

If the speaker is not sure, and is developing a hypothesis, then they would almost certainly use the hypothetical "would".

 

[se16teddy]

As a matter of history, I believe or presume that Egyptians did not sail the Pacific.
Therefore I presume that in the sentence of #1 “navigate” is counterfactual.
Therefore I presume that in the sentence of #1 “would” introduces a counterfactual conditional.
The rewrite of #1 implies that it really happened, and is not counterfactual at all.