[The real answer is in @James K's answer (it's to do with the field of view of your top image being tiny, but the second one is quite wide). This is to translate the situation into one that might be easier to intuitively reason about.]
Let's assume the top photo was taken when Earth-Mercury-Sun is a straight line (this will be very close to true in the top photo). Let's set up the same scenario on Earth, but scaled down.
The diameter of Mercury is 4900km, the Sun is 1.4 million km. This is a ratio of 285:1. Mercury is 40 million km from the Sun, Earth is 150 million km (ignoring eccentricity, etc). Mercury is about 73% of the way to the Sun from here.
A basket ball is about 240mm in diameter. Something 285 times smaller than that is just under one millimetre. That's about the size of a spider mite or a large grain of sand.
In order for the ball to occupy 0.5 degrees of your vision, it needs to be 25 metres away. That's the length of a basketball court, which are probably not in use right now, so lets go down to one. Place the ball under one hoop, then put the spider mite on the tip of the "three point line" at that end of the court. It's magical, so it floats 120mm from the ground. Handily, one hoop's three point line is almost exactly 73% of the way to that hoop from the one at the far end. Now go and lie down under the other hoop and position your head so the mite is in front of the ball from your perspective.
When you look at the tiny mite out there on the far side of the centre line, and the ball at the far end, you have pretty much the same scenario as Earth:Mercury:Sun during a conjunction. Notably, you probably need a telescope to see the mite at all under any kind of normal lighting. Looking at the mite "transiting" the ball though your telescope, doesn't the magnified ball look enormous with the mite floating in front of it like a speck?
Now, go back to the mite and look at the ball from its perspective (don't stand on the poor thing). The ball doesn't look hugely bigger from here, does it? You can probably read more of the writing on it and see the texture, but it's still not taking up all of your vision.
This is because you're not using your telescope any more. If you use the same telescope you used to look at the mite and ball, but stand almost 4 times closer than you were originally, the ball will look even huger.
If you wanted the Sun to look the same size as a basketball does when holding it with the surface 0.5m from your head (2 diameters), that's about 3.5 million km orbital diameter: much, much closer than Mercury really is.
It's twice as close as the Parker Solar Probe will get: the PSP will orbit at 8.5 solar radii, so it'll see the Sun as about size of a basketball that you can't quite touch (just over a metre away).
2 diameter's separation is, however, roughly how Io:Jupiter is set up (Io orbits at about 350000km from the Jovian "surface", Jupiter is 140000km in diameter), so from Io, Jupiter really is huge in the sky, like a basketball in your hands would be.
Metis, at only 58000km from the clouds (orbiting at about 128000km from Jupiter's centre), would see Jupiter like you would if you put your eye about 100mm from a basketball: Jupiter really would fill the sky.