Yes they can.
1. You have to understand that in those days, most of the monitor
uses VGA input.
2. That means as long as your graphics card have a VGA output(there
should be a converter in the box too), you can output the signal
out to the monitor
3. You can visualise it as:
Your old television set have spoilt, so you
bought a new LCD tv. As long as the new tv supports the antenna
input, you can use it to watch programs. Just that now, your
antenna jack is spoilt, as long as you change it into someting that
your tv supports, you can use it.
Note: Older monitors like CRT cannot support HD resolution, meaning
to say you wont see very clear pictures compared to LCD
monitors.
But also due to the lower resolution, the graphics card will not
have to use so much power to produce the same speed of gameplay
when compared to producing the same amount of speed at higher
resolution on the LCD monitor.