There were 40+" CRT TVs (my father got one thrown in for free when he bought his place some years ago and kept usings it because “waste not”) and those things had a big back and were pretty heavy, which makes sense because the entire screen area has to be covered by a single electron gun at the back, so bigger screen means it has to be further back as the angle of the electrons can be made to turn when they exit the electron gun is limited, plus it all has to be happenning in vacuum (so that gas molecules don’t stop the electrons on their way to the screen) so you end up with the whole screen assembly being a big thick glass vacuum shell, so very heavy.
Even the smaller CRT TVs had quite the big back, partly because of the whole electron gun and max angle thing but also because firing electrons in a vacuum requires more than 1000v, which have to be generated from mains on the TV, and high voltages means big chunky components (plus back in the day the components were naturally bigger than they are now for the same capabilities), so even the smaller screen ones were still quite large in the depth axis because of the space needed for high voltage electronics.
Meanwhile the screens for LCD, OLED and so on are basically sandwiches of thin film forming a grid of cells that get activated/deactivated with reasonably small voltages (depends on the tech but if I’m not mistaken they’re all less than 20v) with only the detail that those techs which do not emit light by themselves (such as LCD) need a bit more space for backlighting, all of which can be made way thinner than “enough depth for the electrons from an electron gun to reach the corners of the screen”, much lighter than “requires a vacuum shell for all that space” and then again smaller and lighter because it doesn’t have any high-voltage electronics inside.
There were 40+" CRT TVs (my father got one thrown in for free when he bought his place some years ago and kept usings it because “waste not”) and those things had a big back and were pretty heavy, which makes sense because the entire screen area has to be covered by a single electron gun at the back, so bigger screen means it has to be further back as the angle of the electrons can be made to turn when they exit the electron gun is limited, plus it all has to be happenning in vacuum (so that gas molecules don’t stop the electrons on their way to the screen) so you end up with the whole screen assembly being a big thick glass vacuum shell, so very heavy.
Even the smaller CRT TVs had quite the big back, partly because of the whole electron gun and max angle thing but also because firing electrons in a vacuum requires more than 1000v, which have to be generated from mains on the TV, and high voltages means big chunky components (plus back in the day the components were naturally bigger than they are now for the same capabilities), so even the smaller screen ones were still quite large in the depth axis because of the space needed for high voltage electronics.
Meanwhile the screens for LCD, OLED and so on are basically sandwiches of thin film forming a grid of cells that get activated/deactivated with reasonably small voltages (depends on the tech but if I’m not mistaken they’re all less than 20v) with only the detail that those techs which do not emit light by themselves (such as LCD) need a bit more space for backlighting, all of which can be made way thinner than “enough depth for the electrons from an electron gun to reach the corners of the screen”, much lighter than “requires a vacuum shell for all that space” and then again smaller and lighter because it doesn’t have any high-voltage electronics inside.