Sometimes presolve removes all rows and columns of a problem. When this happens, the log will print the message "Presolve: All rows and columns removed".
The message means all constraints have been removed and all variables are fixed, so there is no need for further LP or MIP solving techniques such as branch-and-bound, heuristics or cutting planes. If the model is feasible, the optimal solution was determined by using the reductions, implications, and propagations that are performed during the presolve phase.