Wealth has nothing to do with "bargaining with HMRC". There is a criminal underpin to HMRC fraud enquiries and the published guidance issued when civil fraud enquiries are opened makes this clear. If a civil enquiry is converted to a criminal enquiry, it will have been because one or more of the triggers for a criminal enquiry were met. There will therefore have been considerably more going on in the background than has been made public. - For reasons of taxpayer confidentiality. Some of that would have become public had the case gone to trial, but certainly not all of it.
Probably Ecclestone and his advisors, who would have had specialist knowledge of HMRC fraud enquiries*, would not have expected HMRC's criminal team to get involved, because of Ecclestone's age. Neither for the same reason would they have expected HMRC to actually take the case to trial. Their bluff was called.
*Anyone subject to HMRC fraud enquiries who does not engage a specialist is doing themselves no favour, because of the criminal underpin of civil fraud enquiries.
In his game of poker with HMRC, Ecclestone would have found himself with an unenviable hand. Meanwhile HMRC's hand would have had at least two pairs, or three aces.
Ecclestone would have the stress of a trial. Even if found innocent, he would still have to enter into a civil settlement with HMRC, because the criminal charge would likely have been cheating the public purse and/or false statements/documents. And if found guilty and Ecclestone is genuinely suffering ill health, he may have been looking to end his life in prison, or a prison hospital.
HMRC benefits from the inevitable publicity of the trial which may deter others from tax fraud. It would also be a warning that age was no barrier to a prosecution. And given HMRC had shown it was not bluffing as regards a prosecution, HMRC really had little to lose. As a result the discussions concerning the (likely) very substantial fiscal penalties and interest, would have been "oiled".
HMG benefits all round. Money flows to the treasury coffers and costs of the hearing are saved. There will be many other times where cases settle before hearings and which remain anonymous.