Complex sentence: BASIC programs often could not achieve acceptable speed animating bitmap graphics, but since this technique only involved moving character objects on the screen, many programs were made this way even on bitmap-capable machines.
Split into simpler sentences: BASIC programs often could not achieve acceptable speed animating bitmap graphics, but since this technique only involved moving character objects on the screen, BASIC could achieve acceptable performance. Many BASIC programs were made this way even on bitmap-capable machines.