Before anyone gives any credence at all to anything that Mahathir may say, I would just like to say a few words of caution.
I am quite sure that Mahathir knows that it all started when he went against Tunku Abdul Rahman (who was until then by his own admission "the happiest Prime Minister in the world") - that was what they wanted after all, power and money.
It was not just him alone, but a whole group within UMNO at the time who went by the name of the "ultras" and who supposedly advocated an anti-Chinese stand (but nevertheless all had some Chinese towkay or another behind them), even today with their "Hidup Melayu!" while at the same time siphoning off as much money as they can through sheer abuse of their positions, both within and outside of government.
This marked the real start of money politics in UMNO and UMNO's foray into business and the corporate sector - so that not very long after the implementation of the NEP, the first victim of UMNO's greed was the very bank set up to "help" Bumiputras, Bank Bumiputra. Many other scandals involving enormous waste of government funds and mismanagement followed, all of which could be covered up under the guise of the NEP and through control of all mass media.
Mahathir himself and his UMNO (also MCA & MIC) cronies who got rich from all the money which they siphoned out of the system through sheer abuse of the NEP - and which was partly used to place him in power to take over as PM and to keep him there for 23 years, as well as to keep the BN in power for so long under UMNO - are largely to blame for all these abuses.
Abdullah and Najib have followed that lead and as inheritors of that systemic abuse are also responsible as serial abusers themselves. The evidence is clear - if only ACA was given a free hand to investigate.
It really does not matter whether Abdullah stays on or is replaced by Najib, as Mahathir wants - and we all know that Mahathir is a man with his own agenda - the national interest being certainly not a part of it. If they have not learned their lesson and continue to abuse their positions, that will certainly be the death knell of UMNO and the BN with it. Then again perhaps that will be better for this country.
However, if Sabah and Sarawak desert the BN NOW, which they should, the people will not have to wait for the next general elections for at least some hope of reform to begin so that all Malaysians can get on with life under more just, equitable and fairer conditions instead of letting all these elites continue to bleed the country dry while the rest of us and the country's resources pay for it.
Whatever it is, don't listen to Mahathir!