WASHINGTON — For the diversity consulting industry, this summer was like no other. Amid the racial reckoning spurred by the death of George Floyd, a wave of senior-level executives began to look critically at their companies, and consultants like Melanie Miller and Loretta VanPelt found themselves deluged with work. Then President Trump stepped in. An executive order, issued in late September as Mr. Trump was stepping up his charged attacks on Black Lives Matter protesters and “political correctness,” banned the federal government, as well as its contractors, subcontractors and grantees, from offering certain diversity training on racial and gender biases...