V=IR
The LDR is pure R (for this example), so it varies say 10K <> 1K. That's all it can do.
When you connect it directly in series from a battery to a transistor, you are just switching the transistor ON !
Even with 10K, in your case, you can't turn it off (Input "current" x beta > Load current).
By putting a 2nd resistor to 0V, you create a voltage divider and change how the transistor "sees" the LDR entirely.
It will now see, say 0.1V - 1.0V (using a 10K LDR, 10K 2nd resistor, and 2V supply.
You have 2 different issues there.