No that's easily derivable from public information about his businesses and the performance of index funds over time. The most knowing how much he spent could tell us is whether he would have been able to spend more or less than he did.
- Case A: Donald Trump runs his companies starting at year X and meanwhile leads a lavish lifestyle, ending up with N1 dollars.
- Case B: Donald Trump puts all his money in index funds and spends nothing, ending up with N2 dollars.
As far as I can tell, you are saying N2 > N1, therefore he would have been better off investing in index funds. But you are comparing apples to oranges if you have different spending habits between the cases. It could be that running his private plane or plating things in gold or whatever would have drained his index fund investment totally.