Monitor as such, is only output device, unless it has a webcam which is input device. So, without a webcam, there's no way someone could "hack" into your monitor to see what you're looking at or who's face is looking at it. If your PC is compromised then any monitoring is made within OS itself, well before the image reaches your monitor.
There are several reasons why the manufacture of CRT monitors ended:
* CRT monitors have bulky size compared to the LCD monitors, which are far thinner.
* It's very difficult to mount CRT monitors on the wall, where mounting LCD monitor on the wall is far easier.
* Due to the size of CRT monitors, it's impractical to build larger than 40" screen monitor. LCD monitors surpass that size limitation easily. I've seen 55" and even 62" single screens.
* CRT monitors are also very heavy compared to their screen size. I had 17" CRT monitor and that weighed at least 5x more than my current 23" LCD monitor.
* Also, CRT monitors waste a lot of electricity as heat, making them very inefficient.
There is no secret reason (conspiracy) why CRT monitors were phased out. That's how technology evolves. Something is invented (CRT) to do something (display information in pictorial form) while when time passes, a better version of same thing is invented (LCD) while the old tech becomes obsolete (CRT).
I can give you plenty of examples of PC hardware evolution. E.g:
RAM - 1st there was SDRAM, then came DDR, then DDR2, DDR3, DDR4 and now DDR5 is in the making.
PCI - 1st there was PCI for GPUs etc. Them came out PCI-E 1.0, PCI-E 2.0 and now, we have PCI-E 3.0 in use in modern PCs.
Storage connections - 1st there was PATA (IDE), then came SATA and it's revisions, now M.2 is thing in PC world.
Storage drives - HDD is oldest, then came SSD and latest is M.2 NVMe SSD.
CPU socket - From Intel side: LGA775, LGA771, LGA1366, LGA1155, LGA2011, LGA1150, LGA1151 (
full list here).
CPU - From Intel side by CPU families: Ivy Bridge, Sandy Bridge, Haswell, Broadwell, Skylake, Kaby Lake, Coffee Lake, (Cannon Lake, Ice Lake, Tiger Lake).
MoBo chipset - From Intel side and Z-series: Z97, Z170, Z270, Z370 where latest is Z390 chipset.
Multimedia storage - Once, there was VHS, which is now obsolete just as CRT. VHS has been effectively replaced with DVDs now.
I think believing in a conspiracy theory is a good thing since it shows you're curious. But if your conspiracy theories make you paranoid and stop living your life normally (where you can go crazy due to it, as said above) then you should either stop using monitors all together or you should change your way of thinking. For example, i'm not sold on the idea that Great Pyramid of Giza was entirely built by humans without any extraterrestrial help and it's use as a tomb. But my life isn't handicapped due to my way of thinking in that matter.