Create Surface From 2 Curves

When I use ExtrudeCrvAlongCrv to try to extrude the circle along the curve which is made up of an arc and a line, the circle does not rotate as it extrudes along the arc. How do I get it to rotate so it does not go flat like it’s doing now?

This is the expected result.
Use instead Sweep1r, it will turn the section along the rail curve giving you the right result.

Or try the Pipe command for a circular section around a center curve. It whichs allow variable diameter.