Because getting hit by a £50m tax bill will force them into administration, RFC were struggling with £30m of debt, if they get hit by the full £50m on top of the existing debt (so totalling £70m or so by the end of this year) it's a totally different ball game, even if they are able to fund it full stop. To avoid it they need someone who can write that kind of money off, is Whyte willing and able to do so?
The key issue with the case is whether the way RFC paid their players (their employees which will be a key point that HMRC will argue in court) via these funds that they set up via a 3rd party was in fact a tax avoidance scheme to reduce their income tax and NI payments. There is no prior precedence in terms of case law as regards this so it's no different to what so called tax specialists were arguing about IR35 related setups before HMRC started winning court cases.