Ecclestone admits to the payment but states he was a victim of blackmail. His lawyers will likely do a great job making it seem that way but it would appear on the surface that Ecclestone paid the banker so that he could sell Formula 1 to the group of his choice. He could then specify his own value and ensure whatever control measures he wanted to make sure he retained control along with future income while cashing out. Ecclestone has a minority share but remains in control of the sport even after stepping down from the board which certainly is interesting.
Delta Topco is the company that currently holds the Formula 1 commercial rights which is itself made up of investment companies. Basically, a bunch of rich people run the show with everyone involved getting their piece of the pie and Ecclestone seems to have manipulated who gets the slices and what size of slice in a manner that benefits him. Not really all that surprising should it be true but it is a question of whether he went about his business illegally.
No trial date is yet set. It certainly is going to be interesting to see what happens.