Develop menu suddenly appeared in Safari

Hi all. The latest in a few strange things that have been happening over the last few days.

The 'develop' menu has suddenly appeared in the Safari menu bar on my Macbook. When I looked at Safari preferences (advanced) the box Show develop menu in menu bar was checked. It's never been checked before, and I certainly haven't changed anything.

A couple of days ago I received an email saying Find My had been disabled on my iPad. When I looked in settings, it wasn't disabled.

Obviously, I'm starting to get a bit worried that I've been hacked in some way.

Does anyone have any ideas why these types of things are happening?

Thanks in advance for any help.