How come my DSLR takes worse low-light photos than my phone, both in RAW w/ comparable settings?

Question

I'm shooting in RAW, manual, on both my DLSR (Nikon D90) and my smartphone (iPhone Xs, Moment Pro camera app) and I've noticed significantly poorer low-light performance on my DSLR, with additional unique problems absent from the phone photos. I use comparable settings, ie.

• DSLR - fully open aperture (f. 3-5-4.5 for most images attached), highest ISO (3.2k - 6.4k), slowest stable handheld shutter (1/60 s)
• Phone - [fixed aperture], highest ISO (1-2k, depending on lens), same handheld shutter (1/30 - 1/60 s)

The devices are:

• Nikon D90 (APS-C), Nikkor DX 18-105 mm f/3.5-5.6, max. ISO - native: 3.2k, extended: 6.4k
• Apple iPhone Xs, wide f/ 1.8 4.25 mm (26 mm eq. ) max. ISO 2.5k, tele 2.4 6.0 mm (52 mm eq. ), max. ISO 1k

Both devices output at 12 MPx (they use different aspect ratios).

The phone consistently produces better results at much lower ISOs, produces significantly less noise, the noise is of less impactful nature, the underexposed areas are true to nature.

On the phone the noise is lumps of mismatched pixels, with the white dots few in between black or similarly colored dots. This makes for an acceptable, albeit heavy-handed crop and a clear full image On the DSLR the white dots dominate the image, making crop borderline unusable and full image still hard to distinguish outlines on, the whole image lacking contrast, being washed out. DSLR also introduces magenta tint in underxposed areas. I'm not talking about contrast edge fringing on objects, I'm talking about huge magenta gradients hundreds of pixels wide in near-black areas.

Additionaly in low light conditions the DSLR loses color depth capture, in extreme cases - completely, only capturing in black and white. No such issue on the phone.

1. Why's the DSLR's performance poorer?
2. What are the causes for each shortcoming of the DSLR compared to the phone? (ie. bigger noise, finer white noise, worse exposure on same ISO, magenta blacks tint, b/w capture in extreme low light)
3. Am I doing sth wrong? I'm using all the relevant settings I can, as aggressively as possible.
4. Shouldn't the DSLR w/ its APS-C sensor, bigger lens and higher ISO range provide far superior low-light performance than the phone?

Samples are edited RAWs, matched as close as possible, exposure brought up as much as noise allowed, exported as 5 MB JPGs.

Edit

To prevent misinfomed answera, here's a reminder: I'm shooting with the phone in RAW, as I stated. That is NOT ProRAW.

I don't get stacking, HDR, multiple sensors' data comparison, noise reduction, sharpening, anything. No processing, computational photography. So yes, I AM comparing apples to apples (phone to DSLR) in THIS CASE. That's how RAW (NOT ProRAW) works on iPhone.

Answer 1

Your DSLR, the Nikon D90, was introduced in 2008 while your cell phone, the iPhone Xs, was introduced in 2018.

So to answer your questions:

1. Because there are 10 years of technology advance between the DSLR and the cell phone.
2. See 1.
3. Probably not.
4. No.

Answer 2

In addition to the difference in technology generations:

You are comparing a fast aspheric prime ("wide f/ 1.8 4.25 mm") on the iphone to a slow consumer zoom lens (in practice, two stops slower, and potentially introducing other image quality problems in super high contrast scenes shot wide open) on your DSLR.