When learning how to operate a system, you want fix as many variables as you can. Each additional variable will make it harder for you to understand, and ultimately control, what’s driving the outcome.
A great example of this is trying to lose weight by both eating less and exercising more.
Not only you don’t know which is the dominating input (hint: it’s almost always eating), but you’re introducing second and third-order effects that make it harder to control the other input. Exercising more will make you more hungry, making it harder to eat less.
What you want to do instead is keep exercise fixed (even if it means doing nothing!) and focusing on eating and seeing if you can use it to drive the results you want.
You can apply the same in business—don’t change your messaging and sales process at the same time. You won’t be able to know which had an impact, if any, on your sales.