Which property of argon and neon causes them to conduct electricity in the gas filled tubelight?Is it because of their inertness?

Neon tubes contain one electrode at each end of the tube. Even though inert gases such as neon are non-reactive under normal conditions, the gas in a neon-filled tube glows if a large enough voltage differential is applied across the tube. The voltage differential creates ionized particles within the tube. These particles conduct electrical current. As the electrons move through the tube, they are ejected from and recombined into the neon electron shells. This process causes the neon-filled tube to illuminate.