ATTiny85 + NRF24L01 integrated board

I attached a photo of the top of the board with components below. The NRF module goes into the female header pins.

I ran across some very strange behavior with this board that's pretty much stumped me. I figured out how to fix it, but I still don't know what the problem was, or why the fix worked.

I was testing this board layout, and it does work, but only if I kept my finger pressed onto the tips of the pins of the NRF module. At first I thought it was a connection issue with a loose pin, but after hours of investigating, I figured out that if I put a 10 nanofarad capacitor from the antennae of the NRF to the ground of the PCB, it works perfectly and ran all day without dropping a single packet.

????BUT WHY????