If the main reason for the Electoral College was to select the best national candidate from a large slate of presidential contenders (for example, favorite sons from each state), what emerging phenomenon in the 1790s eliminated this reason?

The emergence of the party system

Explanation:

The effectiveness of electoral collage depended on the existence of multiple candidates. With the rise of the party system there was no such need as the parties themselves would hold small electoral collages in between themselves and then nominate their best and most popular candidates,

The process remained between two candidates which was not the sole aim of the electoral collage system.

liverpool, trent alexander arnold

explanation:

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.