Moi said that the guy should have been deported to Yemen where his ancestors came from.

Fine, Bahmariz said. I'll go back to Yemen if Moi will go back to Sudan!

They did ascend to power but all disappointed. Both mutunga and justice Ibrahim are former political detainees. Rao, orengo, nyongo, kiraitu all became ministers at some point.

Can we remember anything they did ?

correction :Kibaki was never in the opposition during the agitation for return to multiparty democracy.

You beat me to it. And Kibaki was not even a fence sitter. He was a diligent KANU sycophant. Even after Moi was forced to introduce pluralism, Kibaki said the opposition was wasting its time because trying to defeat KANU was like cutting a mugumo tree with a razor blade.

Kibaki only defected to the opposition in late 1991 when he realized that KANU was unsellable in central province. And some say he spoiled Matiba's chances of beating Moi in 1992.

As to the second question about whether they changed anything, I would say that at the very least they forced moi to cave in and allow pluralism. Otherwise people would still be being beaten and detained without trial.

Being a cabinet minister does not amount to ascending to power. Ministers do the presidents bidding. They do only what the president wants. And sometimes if they are doing too well, they can be removed from the position.

Case in point: Ask anyone who worked at KNH when Matiba was health minister. They will tell you that KNH became very efficient and well run. Matiba would make surprise visits to the place even as late as 1 am in the morning. So the people running the place had to keep ship shape. And how was he rewarded? Moi removed him from the health portfolio and replaced him with Kibaki whom everyone knew was a lazy bum.

Now fast forward to 2002. RAO became minister for roads and and went on a campaign to reclaim land that was set aside for road reserves and firing so called cowboy contractors. It was Kibaki who stopped the process of reclaiming government land.

Wamalwa also became Veep but he was basically reduced to a cheerleader for Kibaki. He had no choice.

Long story short, cabinet ministers are generally powerless to effect the changes that these people were agitating for in the 1990s.
A better measure of someone's ability to effect change is what he does as a governor. I would have liked to see the likes of Matiba or Muliro as governors or even president.