The first factor is response time which is how fast a pixel changes from one colour to another. In LCD they are crystals that need to move physically to change the colour of the pixel (it acts as colour filter of the backlight used in LCD). CRTs and OLEDs don't have backlights and create their own light at every pixel thus don't need moving chrystals to filter anything and so their response times are instant and something LCDs just can not match. But even in OLED and CRTs, CRTS appear much smoother because of the way they display images. In OLEDs and LCDs, the while panel displays the current frame the whole time while in CRTs a beam of time goes from top left of the screen to bottom right in rows. We don't see it as a beam of light because it happens so fast (60 times per second for a 60hz display) and instead see it as a complete image. The thing to note is what is being displayed isn't the complete image but a small streak of light that goes left to right while the whole rest of the display is black (off) and that being black part is what gives it that unbeatable motion clarity (it's just down to how our monkey brain sees things). OLEDs can mimic this to some extent by inserting a black frame after every regular frame which can help to a great extent but still can't completely match a CRT (also it kinda cuts the brightness in half because half the time the screen is just off)