How come The Boy From Oz was such a hit? Peter Allen was (and is) an icon in Australia. THE BOY FROM OZ, the musical was an enormous hit in Australia (where the musical was first staged) for all the obvious reasons. Hugh Jackman, a very popular Australian actor very well-known worldwide for his movie/film work AND with an extensive musical theater background expressed countless times that he would LOVE to appear on Broadway. Producers found the perfect vehicle for him in THE BOY FROM OZ.
Now... the musical was re-written to suit the American palatte of Peter Allen (such as his connections to Judy Garland and Liza Minnelli), so changes were indeed made to the musical to suit the American knowledge of him, etc.
At the time, many questioned why a musical about Peter Allen was ever created for the Broadway stage. Hugh Jackman validated this to many people and the buzz about his performance is what made the show the hit it became on Broadway. The interactive element of the musical's staging is what made the show an experience and many went back to see the show several times (including ever-present diehard fan Barbara Cook). It really had NOTHING to do with his singing or dancing or the book of the show -- it was all about the way he interacted with the audience night-after-night. Each night was fresh. His charismatic personality was something that needed to be seen 'live'.
NOTE: I personally was fortunate to see the show about 6 times. On one memorable night, during the opening Reno Sweeney Act 2 opener, he brought up on stage Elvis Costello (who was in the audience with his mother) after much prompting from Hugh and the audience. Costello joined the onstage band and did a 15-minute impromptu jam session with Hugh (as Peter Allen), the onstage band and the onstage backup girl trio. Things like THAT are what made THE BOY FROM OZ the much-talked-about event of that Broadway season.