Twitter has a payrolled moderation team and while 3rd party apps had benefits an house app without major feature gaps.
Twitter also hasn't grown since making the change - usage has dropped (depending on measurement / estimate) 8-15% and is still dropping.
You're not anymore. The intended audience is _bigger_. It's like how Facebook shifted from young college folks to kids, moms, grandpas, and mainly companies.
The original users of Facebook left, but Facebook still grew.
Now it's Reddit's turn to swap its original user base with a bigger target audience.
And twitter never tried to pivot its core product and kick out most of its users to chase last year's hype and be more attractive to markets that are already happy with other apps.
Their mobile app also incorporated a lot of features and it is not a POS like the Reddit app
It is not so anonymous and real people actually depend on it. Politicans, official organisatons for communication and so on. It is harder to leave it.
Not to mention moderators.