The crystal was mounted that way because we ran out of the 3-SMD type crystal and had to use the 3225 type. The 3225 type (which is what you see in the picture) has 4 pins on the corner, and the crystal is across the diagonal direction (the other two pins are unconnected). In order to use it to replace the 3-pin crystal, it has to be amounted at that angle so that the diagonal pins are soldered onto the two outer pins on the 3-pin footprint. Sorry that it must have caused confusion to you.
CH340C does not need external crystal — it’s a newer version of CH340 that has built-in oscillator (and barely more expensive than Ch340G), so it’s a no-brainer replacement of Ch340G.