I don't think it was mostly motivated by management separation, as much as it was desire to break out revenue and expenses by unit. And this is unchanged.
You're conflating a lot of things here. GOOG class A versus C (GOOG vs GOOGL) dates to a 2014 restructuring of ownership, whereas the Alphabet reorg was in 2015.
Can you break out revenue in a single company? Sure. But you can also easily do it with the structure Alphabet adopted. And, this structure also lends itself to easier valuations of entire units, useful if acquisition of a unit is something being considered.