Lost boost on poison (Trioxin) tower

My team (Croatia ) was 3rd in this conquest event and didn’t get boost on poison tower. I understand that (we need to be 2nd ) and that is ok.

But before conquest has finished we have invested more than 10M gold in that boost to extend it.

One day after ,poison tower boost was shut down.

Why then this option exist when it’s not possible to extend boosts after conquest ends?

Now we have lost more than 10M gold for nothing.