Has the MMR formula changed or become more lenient for lower elo accounts?

Heya, so first of all this is a smurf account, Im decently close to plat on my main, but this was the very first account I used when I started playing league and of course, I jumped into ranked IMMEDIATELY and just got placed in B5 because I really wasnt good at the game.

So the record on the account was like 2-52 or something ridiculous like that because I, like I said, was new to the game and thought I'd just magically get better or something, then when I actually got decent I decided I'd just make a new account, which is now my main. Then I decided, well, might as well see if I can get the old account out of Bronze/Silver.

The record went from 2-52 (approx), which was the record I left it at when making a new account, to 17-59 now (so 15-7) My MMR before going back to the account and doing this was like 180 or something, like absolute cardboard 12, but after playing those games the MMR is now around 600 and says I will rise 2 divisions even though my record and KDAs werent good in the games I played (just tilting because of teammates and I usually played at like 4am)

Now, that was a lot to just ask a question. Did the MMR system become more lenient towards lower elo accounts that show any improvement or something? Like I played absolutely awful in those games, but my MMR went up over 400 from going W-W-L-W-W-L...

Sorry if this is confusing and unorganized.