Why hasn't Queen Liz stepped down and let Charles run the show.....?

Charles is not mentally equipped to run anything.

I think she's grooming William.

She hasn't got any confidence in him?

Because she has said she believes the monarch role is for life.
Most monarchs do !

She's Queen till she dies, that could be another 35 years...lol ;-)

It's hard to give up the crown.

Her brain is still in perfect nick.