It didn’t.
The effect you’re trying to explain is entirely psychological and imagined, and it’s a result of one or multiple changes in both you and your environment:
- you’re playing less than you used to, so you are worse, so your opponents seem to be better than usual,
- the meta is unfavorable for your style of play/knowledge, which truly makes your opponent better than usual compared to YOU, so in a way, you ARE on your way to lower your MMR, but if you play for long enough, seasonal changes will be incorporated into the memory of your MMR score and affect your MMR less and less.
Final effect is a result of the sample getting better, I suppose, so when calculating the new total MMR, bigger numbers of games included in calculation of the MMR should lead to lower relative changes to it.
EDIT: For those versed in complexity science, his highroll rank of 350 is an attractor, and it’s in conflict with his current MMR, which is also an attractor, but this one has the benefit of gravity because he’s already IN it, in a sense. So it takes a large external force to get him out of that one, into the 350 attractor and stay there for long enough until his MMR is fixed to the new attractor.
For some weird reasons hard to explain with common sense language (or rather, I don’t know how), if you only once approached and “sensed” the 350 attractor, you might get repelled by the difference in potential and energy it takes to operate on that level, and the repellen effect usually makes you adapt to the current MMR level of play as a defensive mechanism, so it takes additional mental power to even attempt it.
For me, when I broke off my 1k attractor and got inside the top 200 one, external force to help with push was the desire to see myself on streams xD
Now that’s been done, it is no longer a sufficient motivation, aka, adequate external force.
TL;DR Anyway, the point is, it’s hard to break out of your MMR, one way or another. It always requires significant external force or targetted motivation.