This study aims to examine whether the diversification-strategy dynamics implemented prior to the COVID-19 pandemic were beneficial afterward in six major global companies included in the Fortune 500 list: Apple, Shell, ExxonMobil, Amazon, Toyota, and Volkswagen. It also investigates whether the effects differ between interrelated and non-interrelated diversification strategies. The study assesses this by testing the correlation relationship between the companies’ revenues in the twenty-first century, specifically for the period from 2010 to 2024, using Pearson’s correlation coefficient. Data were collected from the Fortune magazine website. Using a case study approach, the research examines the revenues achieved by the selected companies during the specified period. The study reached several conclusions, most importantly that the diversification-strategy dynamics prior to the COVID-19 pandemic were generally not beneficial after the onset of the pandemic.