Maxene Fabe covered this in her book. Bud Grant of CBS called Mark Goodson and told him he was interested in bringing TPIR back as part of a new AM GS block in Fall 1972. But Goodson eventually discovered the original format wouldn't work "these days"--too boring and too slow. He contacted Grant and told him that "unless you want a whole new show, we're going to have to cancel our deal", to which Grant replied "No, go ahead, I trust you. Overhaul it from top to bottom if you have to." And the rest is history.
Lucky thing I was a 17-year-old high school senior at the time and not in Grant's position. If I'd been in the CBS honcho's position then, and Mark G. told me that I'd have had to agree to a whole new SHOW, I might have turned him down, assuming as I likely would have that Goodson might have meant a new, NON-TPIR show instead of a whole new TPIR, and the world would have been deprived of a future classic. There'd have been no Bob Barker Theatre at CBS.
I can't completely agree, though, with Fabe's assumption that I'd be bored to tears if I were to watch the original version today. I'd love to see the old Cullen shows today, and on the off-chance one or two color tapes ever survived to today, that would be anything BUT boring to watch.
As for Plinko as a stand-alone game, four words: big plastic home version.