Poor countries have less capital. Thus the cost of money is high. For example in Uganda a bank loan costs 20% interest. At such rates only the most effective investments are viable.
Many countries in Africa have such large room for improvement through investment. Data centers are not the biggest need. For example in Uganda they grow avocado's, but lack the cold chain distribution network to sell into the international market.
Thus you have avocado's selling for peanuts at local markets instead of earning big money selling to the west.
Building up a nation's capital stock takes time and long term stability. Thankfully Africa has the stability but time is slow.