The reason is related to national security. Trump said there was a "real threat" behind Broadcom's acquisition plan by Broadcom. Broadcom is a Singapore-based foreign company and Qualcomm is a US company with a number of important technology patents.
If it can control Qualcomm through acquisitions, Trump alleges that Broadcom will take steps that endanger US national security.
Executive orders from Trump did not elaborate on exactly what threats to national security from Broadcom's acquisition plan by Broadcom.
Previously there was concern that Broadcom will sell Qualcomm technology to other parties from countries outside the US.
There are also allegations that Qualcomm's performance will weaken under Broadcom, so its rivals such as Huawei from China can be more dominant, especially in the development of 5G technology in the future.
This concern is also the concern of the Committee on Foreign Investments in the United States (CFIUS) which compiled recommendations for Trump regarding the acquisition plan.
Last February, Qualcomm rejected a $ 121 billion acquisition offer from Broadcom. But Broadcom would not give up so easily and keep pursuing Qualcomm.
Broadcom wants to change the composition of Qualcomm's board of directors with the people of their choice through voting shareholders. As a result, Chairman and founder of Qualcomm's son, Paul Jacobs lost his post last week.
Broadcom also announced it would move its office from Singapore to the United States in early April. This move is thought to pave the way for taking over Qualcomm, because it already smells suspicion CFIUS.
Business agreements between two equally-derived companies from the United States are outside the jurisdiction of CFIUS. But unexpectedly, the US government acted faster by issuing an executive order.