Impossible. Bridges charge per use and people still use bridges! Twitter is like a bridge, but instead of connecting roads it connects people. Also, there are pay-per-use toilets, and twitter is like... well you get it.
Of course! Because that other bridge is free only in a monetary sense but the twitter bridge will be free in a speech sense. Can't say racist/homophobic/anti-Semitic/misogynistic/hateful things on that on that other bridge? Do the moderators on that other bridge frown when you try and spread false stories about recently attacked politicians? Well on twitter bridge, you pay the fee and say all this and more! There is so much hate and craziness out there right now. People intensely wanting to say hateful and crazy things to other people. Why not monetize it? Billions to made! Billions!
This will reduce crap spam content because it will cost too much. Even regular users will tweet fewer bla posts.
Win-win!