What's The Reason For CE's Low Movement Speed?

In a era where we had fast paced shooters like Doom, Quake, GoldenEye 64, Perfect Dark, Unreal Gold, Unreal Tournament, Turok, Timesplitters, etc, why was Halo’s movement speed made low?

I assume it was likely done for strategy purposes so that you couldn’t run away from battles.

It was done due to making a shooter that was controller first. Of the list above, most of those games you mentioned were designed for the precision of PC’s. CE was done so that it was easy to jump into without needing to be an expert to play the game well. Of course, controllers and players skill have introvert drastically, and now you can play extremely fast paced games like DOOM Eternal on console extremely well even on extremely high difficulties.