Mac OS needs password for your gmail account

A popup "Mac OS needs password for your gmail account" appeared. I entered my password for that account, then got an alert message from Google asking if it was me who gave that access. This happened on the Chrome browser.

I had the day before reset the password for that gmail account because when signing into a web site I was asked for my password, which I gave. Afterwards I got an alert from Google that the password for my gmail account had been changed. Very mysterious indeed! I wondered if perhaps in my haste I had unknowingly given permission to a hack, so I changed the password for the gmail account.

So when I got the popup "Mac OS needs password for your gmail account" I thought it was Gmail or Thunderbird (I use Thunderbird to auto-sync Gmail onto my desktop) needing to complete the password change. But now I wonder.

Is this legitimate, required? Google is very confusing, very difficult to deal with in making/changing account settings (I use it, though, so I can have a consistent address, even if I need to change ISP). It's really bugging that it sends these alerts then makes it so difficult to deal with. Do I really want to change my password again and then go thru all this stuff another time!?

Again, is this "Mac OS needs password for your gmail account" request legitimate, required?

Thanks, in advance, for help.