Business investments have always been a deductible expense. The idea that by saving rich people money, they would invest it in their business, is obviously bullshit; they can just invest the money and not be taxed on it anyway.

It's doubly bullshit given that businesses are also separate taxable entities. Don't take the money out of the business if you don't want it to be taxed as income; invest it back in so it becomes an expense, and neither you nor the business (effectively) pay taxes on it.

So, no. Even with a solid industrial base, "trickle down economics" was still just as obviously bullshit.