Stupid ass jack!

Drag this to your bookmarks bar: Hangouts Grid View

and then navigate back to your hangout and click the bookmark you just created. (Tested in chrome.)

This is the code:

function addStyle(styleString) {
  const style = document.createElement('style');
  style.textContent = styleString;
  document.head.append(style);
}
addStyle(`
.p2hjYe.rCuEk {display: none;}
.gSTPzb {  position: fixed !important;  top: 0;  left: 0;  bottom: 0;  right: 0;  overflow: visible;  display: flex !important;  flex-flow: row wrap;}
.gSTPzb > * {  flex: 1 0 25vw;  min-height: 25vh; }
.Wmf6nf, .Wmf6nf * {  height: 100% !important;  width: 100% !important;  top: auto !important; }
.ZEZETe.HQYS7 {  outline: 2px solid teal;  z-index: 5; }
`);