Getting more thinking time tends to give surprisingly small improvements to playing strength. For a classical alpha-beta search based engine, for a given ply (turn) you might have ~20 moves to consider each depth of the search tree. If you're trying to brute force search deeper, a 10x increase in compute time or power doesn't even let you search an extra ply.

Elo gains for engines tend to come from better evaluation, better pruning, and better search heuristics. That's not to say that longer search time or a stronger CPU doesn't help, it just doesn't magically make a weak engine into a strong engine.

There is a strategy called alpha beta pruning meaning you can discard a lot of move options quickly based on the results of similar branches. That and caching similar board states means 20x options does not mean 20x CPU time.