This is in my thoughts on the YT algorithm. I have run multiple kids channels and at a few points, my views went from 100k/day down to like 5-10k. Then wait a few months and I got put back into suggestion and it can have 250k/Day. I even tried this. I uploaded a video to my "old channel" got 5k views in 3 days and then died... Took it down edited it a bit and uploaded to a new channel. That video got 1m views the first 20 days

Youtube has a limited amount of views and a lot of content can be similarly entertaining to the same audience so my guess is your channel gets switched out and someone else's pops. Then in a while, you get back in and someone else gets his/her channel views hammered.
I have now run 3 channels in the same niche for about a year and 2 are competing directly. If I upload a video with similar content on the other channel with targeting keywords, my suggested views for the other will go down while the others go up. Seen it a hundred times. BUT a note here is that this has enabled me to hedge against this. I have seen 1 time where views on both my channels go down at the same time and that was for a short period. Calculated I get about 1.5 times the amount of views I got with 1 channel now with 2 because of the fact that one is always performing. Sometimes they both go on a spree at the same time and I can get around 300-500k/day, not like that gives you any money these days. I´ve pretty much stopped with YT for now and focusing on my sites instead until I have recreated all the channels content on other languages and I can hire someone to animate them for me because the kids niche is like avg 0.15usd per 1k views which is horrible

Not worth spending 30hrs on a single 8-minute video. In my niche thumbnail is king and I have to get around 25% clickthrough to have a video go. But mine does never fall out either, I have my first videos on both channels still accumulating millions of years each year so for our niche, it adds up. But I also see YT doing everything they an to move ads from creators videos to other ad placements on the site so that they don´t have to share the revenue

That has been going on for quite some time and I see it escalating. We now have top video position as an AD in a few years the top 3-5 will be ads and they will be even more ads throughout scrolling. Its a pretty shitty platform these days and the earnings per 1k views have been dropping drastically over time. Not including COPPA in my calculations there.*
EDIT: PS I wrote this on my shitty phone so sorry for all the errors!