The short answer is no, there is no TATL overcapacity this summer. In fact, TATL flying continues to suffer from under capacity during peak season as the Euro carriers retired many of their larger birds during the pandemic.
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That said, in any environment there's always a little distressed inventory which airlines will seek to sell at bargain prices. Most people flying TATL this summer bought their tickets long ago, so last minute sales like the deal you bought are essentially icing on the cake.

FWIW, on TPAC I'm benefitting from the same phenomenon, having recently bought a $2500 OW Z-fare ticket WAS-TAS on DL/KE for August. Flights to Asia this summer are similarly full, but again, a sale on a lightly traveled city pair is essentially gravy.