I am trying to import architectural interiors from online 3d model marketplaces like CGTrader or Turbosquid. My workflow is that I download the fbx file, corresponding textures file and put it in a folder called textures at same level as fbx file. Then goto Blender and import the fbx. What I get after import is always a mesh with no textures applied and totally unlit. No matter whether I choose rendering engine as Eevee or Cycles, the textures never get rendered. In the Shading preview (in lookdev portion), the interior is always dark, even then there are lights included in the downloaded fbx.
For example, consider the free 3d model available here: https://www.cgtrader.com/items/1883142/download-page
I download the bathroom.fbx and texture.rar. Then created a folder and placed the fbx inside the folder and also put the texture folder extracted from texture.rar here, at same leves as .fbx (see in the screenshot, my folder structure 
) and here is what I see in Blender 
As you can see that in the Viewport Shading using Cycles, the whole interior is dark and with spots like its still rendering (even though Blender completed by saying "Rendering Done").
Here is how it should look like:
What am I missing?
If it helps, I am using Blender 2.91.
