Nderitu was certainly a billionaire in 1990s - in 80s he was surveyor living in South B. He probably made his money through Wilson Gachanja the powerful corrupt land commissioner and gov supplies.
Rigathi was student in 80s - and DO in the 1990s.
Rigathi Gachagua was mtu ya mkono for Moi, his bro and Prof Mbithi in 1990s - while working n gov. Working for Prof Mbithi the head of public service must have brought him to real corridor of powers.
Ruto meet Uhuru through Gideon Moi - as Ruto was worming his way to Moi's Kitchen cabinet through Gideon - and so was Uhuru working his way up in KANU through Gideon. Gideon in last term of Moi had effectively become the gatekeeper and statehouse comptroller - and the power man - firing and hiring - while protecting their father - Kuleis and Biwot were being hunted for cheating mzee and being told to return Mzee wealth.
When did Gachagua meet Uhuru....I think in early 2002...when Moi had become serious in the bid and needed someone strong to keep Uhuru on a tight leash.
During that period btw 2002 to now - Ruto and Rigathi must have met so many times as they tried to both keep Uhuru on the narrow path away from drugs.
I bet for the last two decades...Ruto and Rigathi first word...Mdosi amekunywa ama bado...okay tufanye kesho. Chunga asikunywe mapema. They have both been mothering Uhuru. Silently Uhuru resented this - and during his final term - unleashed on them.
Gachagua have been billionares since 80s .He happens to be a Moist who Ruto can closely trust.
Now about his attacks on Uhuru , Gachagua is one of the reason in 90s Ruto believed in Uhuru. The world is Round.