How is it possible that Opera got all my saved passwords and sh*t from Chrome?

I did not authorize this during install.

Unless they stopped since last time I checked, they also insert sponsored stuff in your bookmarks at each update.

Wow I didn't realize that. That's incredibly intrusive.

You probably clicked Accept and Install. "Import bookmarks and data" is under options in the first screen of the installer and ticked by default.

Could be... but the design is such, that almost anyone will do that not knowing what it all means.

This could be said about almost any technology.

Just because you did not look at the settings does not mean there was no option. I get this from the elderly all the time, "Well how was I supposed to know to click that menu first?"

I think it uses Chrome's codebase, including the secure storage locations.

Regardless, this shouldn't be possible.

Chrome is supposed to tie them with the single instance you're running. You can't just copy the Chrome folder and transfer it to another location. You'd have to use Chrome's Sync for that. I'm assuming Chrome has been opened at the same time by the OP, allowing Opera to snatch the passwords and other shit, making an intrusion into Chrome's data.

But, on the other hand, I was able to copy the data from a Chrome extension after a system crash on one machine and extract the data to a new machine just fine by reinstalling the extension and then pasting the extension's folder to the same location where it was on the previous machine.

Since that extension was Mailvelope, I would essentially lose a private key in this case if that wasn't possible, since I didn't have the backup of it. Not sure if I would call that bug or a feature.

I did have Chrome open at that time.. that is true.

But still... this is some weird sh*t... they should have at least asked me before.

They did, you just did not read what you were accepting when you "Accept[ed] and Install[ed]"