What is your goal specifically?, many of us in here we don't understand you really, do you want international companies to open their offices in Tanzania like they do in Kenya, or do you want investors to invest in Tanzania?.
Tanzania is leading by far In this region as the best investment destination, Tanzania receives more FDI than almost all other east African countries, just USA alone invested $1.5B in Tanzania while it invested only $353M in Kenya, $42M in Uganda, $11M in Rwanda and S1M, remember USA is not in the list of top 5 investors in Tanzania, China, India and UK top the list.
Remember that every country has different environment for different investors, Nairobi because of its History, climate, easy for international flight connections, capitalism and strong private sector with weak government sectors, offers good environment for opening offices and shelters for westerners and rich people, on other hand Tanzania with it's Natural resources, peace and stability, strong government stewardship, Geographical position and strong foundation of political stability, offers good environment for investments, this is exactly what is happening.