The 2004 Nadal was really fun to watch and his mindset was completely different from what we've been witnessing since 2005. Still remember his match against Hewitt in Australia that year, there was a kid who went for his FH whenever he had a chance, who was receiving serves while standing on the baseline and who was extremely aggressive returner (the difference between this and their 2005 AO match was enormous). He was very entertaining player back then, at least to me.
I don't know why he decided to give up on power tennis and start playing physical tennis, but with 16 Majors in his pocket...well, it's hard to argue against it. The sad thing is that I believe he would've been as successful had he kept his aggressive mindset (and would've been more fun to watch

).