Garmin IQ Store support team.

every time you update the app, the app gets moved to the last page. when people pull in the update you get the downloads back so in a day or 3-4 you should be back where you were.

In did, today I’ve made update for w/f.
Now all clear. Thanks a lot)

Like Peter said, "most popular" is based on downloads for the current version, so if you update an app, it will drop back in that ranking. There also seems to be something involving time too, where it's based on downloads of the latest version in the last X days, so even if you've not done an update, if downloads taper off, it can move back over time. You can always tell when one of the apps that are consistently in the "most popular" on the main page of the store get updated, as they are off that list for a while, but usually come back quickly.

Another thing involved is "auto-migration", where you might not have sent an update, but the store created a new version for a new device or something like an APAC variant of a current device (you'll see your version number has -updX at the end). This also resets the ranking as it's a new version.

I see.

Regarding auto-update I know.

Regarding drop down, imho, it's done to give possibility for apps with less rate to show itself.
However, very seldom people going down up to last page. Means – each update of apps makes it less downloadable for new people and more isolated between old users.
However, I’m not making money from this, let it be as it is.

Thanks for as usual good and detailed explanation)

Some of this can be minimized on how you do things. As an app matures, you probably won't make many changes to it (I updated one that I'd not updated since 2015 not long ago)

You may find you want to batch your changes to minimize updates. If you have 3 changes, don't make a change and update, make another change and update, etc, but make the changes at the same time and update once. That 2015 update I mentioned involved a bunch of changes, but I uploaded then all at the same time.

All noted)
Thanks for advice)

This method of calculation is contrary to the principles of DEVOPS, where it is necessary to make slight modifications slightly impacting the user with each change

Honestly, I do not see any common or useful sense in type of calculation.
Almost all of my updates were answers to user’s requests, maybe except 2 or 3.

So, as per this calculation idea, I have to ignore users request, or wait for a year, make huge update and anyhow became at last page?

This type of calculations – nonsense but we have what we have.