Argentina’s runaway inflation is caused by the central bank printing money (to finance the government’s out of control spending). The rationale for dollarization is to remove the ability for the government to do this. It’s not an inherently crazy idea, since (i) there are smaller Latin American countries that use the dollar, and (ii) the dollar is already used de facto for many purposes in Argentina because of how debased the peso has been. But there are lots of practical problems; notably, Argentina simply does not own enough dollars in the entire country to keep the economy running normally if they switch (whatever “normally” means for an economy like theirs).