I think they chose Sakura for the sake of Publicity
"Any publicity is good publicity," apparently. They are aware of the hate and comparison clips going on about Sakura, and they are using that to their advantage. Tbh, all I see are contents about "who they eliminated(any contestant in prelude) vs who they debuted (Sakura)". At this point, all eyes are on Sakura.
I was rooting for Ayana, especially since I have watched her grow from GP999, even though debuting her to prelude "makes sense", the producers probably think that it would be a "boring route", and was too predictable. They know that the public is always scrutinizing Sakura, and they are trying to make a narrative about it.
Because she was chosen to debut, there will be people who will constantly criticize her, there will be people who will defend her, there will be people pointing out her improvements, and someday soon(once she's more improved and established), she will have fans who will say, "So this is why she was chosen". Sakura will always be a topic for discussion, and it leads to publicity.
Right now, everyone is concerned about debuting a child and how she creates an imbalance in the group. Again, a topic for discussion always leads to publicity.
The thing is, producers don't care about what the audience wants; they don't even care about Sakura's mental health, that she gets so much hate, and heck, they don't even care that she's a literal minor. All they want is money, and publicity creates money.
I wish all the best for Sakura; she seems bright and bubbly, and I hope everyone becomes kinder to her. She does have potential, and I hope that the industry doesn't abuse that.