Ythrians And The League

Ythri was discovered during the Grand Survey long before the founding of the Polesotechnic League so why does Hloch write:

"The Polesotechnic League we know of only in its decadence and downfall."
-Poul Anderson, INTRODUCTION to "Margin of Profit" IN Anderson, The Van Rijn Method (Riverdale, NY, 2009), pp. 135-136 AT p. 135?

Hloch explains:

Ythri is remote from the centers of Technic civilization;

the earliest visitors were occasional merchant vessels, scientists, hired teachers and consultants;

few Ythrians visited Terra;

when the Ythrians began their own regular space travel, they no longer needed imports;

they competed so successfully for trade with nearby planetary systems that League merchants withdrew from what had never been a highly profitable region for them;

the nearest point of contact for the League was the thinly settled Esperance which drew little trade from either side.

Hloch asks:

"What winds did Falkayn ride, what storms blew him hitherward at last?"
-op. cit., p. 136.

Hloch writes in Planha. Wind and storms are the winged Ythrians' environment.

Of van Rijn, he writes:

"He did truthfully fly in the front echelons of events when several things happened whose thunders would echo through centuries." (ibid.)

Powerful language. Ythrians fly through skies that sometimes echo with thunder.