landmark1234 appears to have the idea but is struggling with the behind the scenes "why ?".
The other part of the equation is wing strength. In its simplest form, that depends on some sort of spar structure to hold the wing together under load. A spar is not dissimilar, in principle, to a bridge beam. Depth has a very much higher influence on strength than, say, width.
First, we need the wing thickness to hide the spar bits which stop the wing falling apart.
Then, we cast around for ways to moderate the undesirable effects of the wing thickness on airflow.
Hence - wingsweep to take advantage of thickness:chord ratio determines the speed at which shockwaves form
why do swept wing aircraft fly with higher nose up attitudes ?
Faster aircraft wings are designed to work best at high speed cruise. However, those aircraft still have to land and takeoff within sensible speed ranges. To get the lift needed at the lower speeds, they employ higher incidence (usually along with LE devices to permit those higher angles) .. hence comparatively high pitch angles on takeoff (especially) and approach and landing.