It may be cause of Forza Horizon 4 coming out in the same week. As of that week FH4 ultimate is already out, and it would be in the this chart, if they didn't chose to group it in with the standard launch.
The last entry sold exceptionally well in the UK, and this time the game is set in the UK, and marketing has been more aggressive in general.
To add to that, PS has the Fifa marketing marketing, as well.
But doesn't forza generally have modest sales at launch but long legs thanks to bundles and various discounts?