Garibaldi could easily have

kept the Kingdom of the Two Sicilies with himself

as king. Why do you think he turned over control

to Victor Emmanuel II instead?

Answer: monarchy was still the most common form of government at that time (2nd half of the 19th century), i. e. republicanism was not very popular and frequently viewed as destructive. Don't forget that in Italy itself republican regime was established only in 1946 (after the referendum) : majority for republic was a narrow majority. So-called 1st republic lasted from 1946 to 1993.

Explanation: Garibaldi was not a republican politician and Savoy dynasty (even though it was not of Italian origin: today Savoy makes part of France, in Savoy French was always spoken, temple of Savoy dynasty is in Chambéry which is in France) was probably the most suitable.