Final answer:
Syrians were no longer welcome in Egypt primarily due to historical resentment stemming from past occupations and the lack of democratic reforms leading to political instability in Syria.
Step-by-step explanation:
The two main reasons Syrians were no longer welcome in Egypt relate to historical grievances and current political unrest. First, there is a deep-seated resentment towards Syrian occupation and influence, which predisposes the population to displace their fears and hostilities onto Syrian refugees.
Second, the lack of democratic reforms, high unemployment, and the loss of civil rights as a result of the Syrian government's actions, including the lengthy state of emergency declared in 1963, have contributed to ongoing political instability, prompting protests and dissatisfaction, likened to those during the Arab Spring.
The Mamluk sultans' treatment of rebellious Syrian Arabs more leniently than Egyptian Bedouins can be attributed to the strategic need for Syrian Arab assistance to repel Mongol and Ottoman attacks, highlighting a historical pattern of pragmatic alliances despite underlying tensions.