Safari small screen on opening

When I open Safari on my MacBook Air or then search for something on the internet, it appears as a very narrow strip across the screen, occupying only about 1/4 of the height of the screen.

I have Monterey 12.0.1 and I think this started after I'd updated. It always used to fill the screen on opening, by default. Easy enough to click 'Enter full screen', but it would be more convenient if I didn't have to.

I've seen a few suggestions in earlier discussions but can't get anything to work. The suggested answers I think pre-date Monterey ~ is there a way of making the Safari page open full-screen by default again, perhaps unique to Monterey, please?