In the 90s, I tried playing the demo of this game many times and could never really get into it. Crusader was one of the best looking PC games of its time and I really wanted to like it. But the controls. Oh my God, the controls. Eventually, this scheme would go on to be described as tank controls in other games like Resident Evil. Basically, you aim and move your character in relation to the direction their sprite is facing rather than the direction you want them to move on the screen. Crusader takes that counter-intuitive mechanic to a whole new level of complexity by adding jumping, diving and ducking to the mix.
There are some default mouse controls which almost work, but your character is stuck with gun drawn, shuffling around like a man with his pants around his ankles. I got about a third the way through the game doing that until just gave up and set the game aside for a while. Months later I returned and forced myself to learn the standard keyboard controls. These are still clunky, but with practice and a lot of help from the auto-aim feature the game becomes much more fast-paced and responsive. Even then, the mouse is still helpful when the occasional fast-spinning aiming is required. For the most part, it pays to just bite the bullet and learn the keyboard controls. Think of Crusader like Mavis Beacon Teaches Typing but with more explosions and incinerated humans.