I know people complaining about panic buying but then completely changing their shopping habits and going in early to do a bigger shop than they normally would
It's normal and understandable to want to be able to get your shopping in but if everyone is doing that it's contributing to the empty shelves as much as panic buying. Not being critical of them, just everyone changing their shopping habits is going to be hard for the shops to suddenly adapt to
To me, two things have happened here.
Firstly, there was totally unnecessary panic buying early on. This was the lighting of the blue touch-paper.
Others see the panic buying then feel compelled to also go out and get stuff in before it all goes. This fuels the problem further. Others who were shopping normally are then compelled to grab what they can too. Eventually, everyone is panic-buying to some extent or other.
Secondly, as the crisis has developed, social distancing has become so important. This means people will feel the need to buy more items, but in fewer visits to the shops. So, less visits in order to expose less to the possibility of infection, but as much shopping in the trolley as people can get hold of and/or afford. Also, many of those who would still like to shop responsibly are feeling compelled to grab what they can because they know if they don't, the panicking locusts will buy it all instead. It's a vicious circle, that once rolling, is difficult to stop.
As far as I'm aware, there are still no actual shortages of things, so if the initial panic buyers had kept their heads, there would be little in the way of problems getting hold of anything you need. Those knee-jerkers and scumbags who bought stuff in bulk to sell on at a profit in the crisis have caused this whole mess at the shops and should be ashamed of themselves.