You seem to have written your post based on the assumption that people here don’t understand the reality of the situation but they do 
As Kieran’s said, it wasn’t necessary to use crowdfunding for this latest raise.
Institutional investors are essential at this point because of the large amount of capital that needs to be raised. But crowdfunding investors are powerful advocates for Monzo. Lots of Monzo’s growth has come from word of mouth referrals.
I’d like to think that Monzo cares enough about it’s users to give them an opportunity to invest in it’s success. I’m not aware of real downsides to that approach, assuming institutional investors are included in the round, which they have been.
The crowdfunders know this..
The value of crowdfunders investments from the round before the last increased by over 50% this round.
Because they’re intelligent & have a sustainable business model.