The little tiny fans in the laptop will typically be able to move a small amount of air with a large pressure. The fans you have used here externally will be able to move a large amount of air with a low pressure, but since you're trying to cram that air through a small space, they will actually be able to move a minuscule amount of air with that same low pressure. That's probably mostly why you aren't seeing much improvement.

I'd say that you have two options.

The first is to try to use external fans to force more air through the laptop than the internal fans manage. You'll need high pressure (probably centrifugal rather than radial) fans to achieve this. They'll be noisy.

The alternative, which can use quieter low-pressure fans like the ones you have, is to just ensure that all the air going into the air intakes on the laptop is as cold as possible. That is, make sure the air going in hasn't just come out. And make sure there isn't any more restriction on air flow than the minimum possible, which the raised gap under the laptop will achieve. You basically just want to direct fresh cold air from far away from the laptop towards the air intakes, and pull the air emerging from the air outlets as far away from the laptop as possible. A horizontal breeze flowing across the bottom of the laptop is probably one of the best ways to achieve this.