Really over the top and hideously superficial article. Doesn't say why the Merlin was so important beyond the fact of its development, which probably happened with many other engines too.
Was it the power to weight ratio? The low volume compared to other engines? Power available at a certain height? Low consumption? Why did it work so well compared to the Alison in the Mustang?
Installing the Merlin in the Mustang was Ronnie Harker's idea and he was a Rolls Royce test pilot.
I guess the article wasn't aimed at an aviation audience.