Hunterboy, with what greater felony, as you are using the US as an example, do you imagine he was charged?
To bargain, you need to be convinced that at trial, you will be found guilty of the greater offence. The bargain is in the fact that you plead a lesser offence to save the cost of a trial and also, crucially, to get a reduced sentence.
So if he pled (or is it pleaded?) not guilty, went for the full trial, got found guilty, just what sentence do you imagine he would have got?
This is the UK, not the wild west.