They pretty much wanted another full price payoff at the expense of supporting the existing game. When the lootbox laws tightened and they became less appealing, the game really stalled in monetisation options and then they made the knee-jerk decision to make a full-blown sequel which is basically an expansion with a PvE element which all could've been integrated into the basegame over a period of years instead. They could've easily made this content into a £20-$25 season pass which would've brought people back, kept existing users playing and seen them make steady income.
It's another dumb decision from a shite AAA publisher. There is a huge gaping hole in their content across all games and it's no wonder they are losing millions of players and that's without the recent bad PR.