We don't hate your main account, your main account, your main account had already settled and the MMR system made a determination of where you were at. It likely thought you were G2, and thus you need to win enough to pull you away from where it determined you were at. If you won 50 games in a row at G2, you would easily make it to P4, right? But you likely were sitting at a 50% WR, which means you aren't going to climb.
If you buy a new account (depending on its MMR when you buy it), it would have more variance and thus you likely are getting more LP gain because it's establishing your skill and likely saying "OK, this person is a lot better than where they're currently at". I forget the exact #, but it takes a number of games before your MMR settles and you need to do more to pull away from that settled state. Also, as someone who is trying to climb in ranked and thus has been playing a lot more, you likely got A LOT better from playing 700 games, and you carried that ...
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