When interest rates were rock bottom, the present value of the future cashflows from streaming, royalties, etc. would have been higher and the price of the catalogues more expensive = big pay days for Bob and Bruce; great timing.
Unfortunately, Genesis are selling just as interest rates are spiking upwards so they won't get as much as they would have done.
£300million invested at old 1% rates is £3 million a year ! They would always get much more than that.