Was Stephen King inspired by Dean R. Koontz?

If anything King seems inspired by Rod Serling and his small-screen classic "The Twilight Zone." So many of King's stories resemble the tales Serling green-lit.

He was heavily influenced by Lovecraft I would imagine.

It's been said that the real influence on his life and career was his father walking out on the family when he was young.

didnt koontz start releasing after king parved the way for horror literature

Koontz was publishing novels before King, but what he was writing was very different. I've read a few of the early novels that were science fiction/fantasy but not much of the stuff that may have been horror... I still remember "The Haunted Earth" as an entertaining romp - kind of like Clifford Simak writing a hardboiled detective story with aliens and supernatural monsters. And "Demon Seed" (filmed in '77) was not bad. "Invasion", the one I liked most, was published by Laser Books under a pseudonym and was about a Nam vet in a remote cabin being threatened by aliens - and I didn't even know it was by Koontz for decades.
When King hit BIG with "Carrie" and "Salems Lot" in '74-75, the marketing of horror novels changed fast to capitalize on King's success and Koontz various new novels were part of the change. I just looked it up and realized that Koontz was still publishing under a number of pseudonyms for several years. It wasn't till the '80s that he became a familiar name on horror novel covers. So, maybe King read some early Koontz, but I'd say, if anything Koontz was inspired by King - or his marketing was, anyway.

This is just another example of a drag queen

I doubt it. Of course, you know that King and Koontz collaborated on two novels - "The Talisman" and "Black House"