the standard as far as biopics goes
has always been to cast a relatively uknown in pop culture- rock star roles
and cast an elder actor or actress in statesman type roles that hope to garner the public's respect.
Joe Orton played by a very good young newcomer Gary Oldman
Sid vicious- Gary oldham again, both when he was relatively new to starring roles, infact his first.
Elvis - a upcoming Kurt Russel- his farst major and star role
before that in bit parts in disney features
Ray Charles- Jamie Foxx second main star role
whereass for politicions and royalty
older stars are used to give off an air of respectability and wisdom.
The queen- helen miram
queen voctoria judy dench
margerat thatcher - Meryl streep
Nixon anthony - hopkins
you get the idea.
for pop culture it is best to cast a upcoming relatively uknown face who can be the person for the audience to believe in the film
for in pop culture image is everything.
In royalty and politics
a sense of grandfathliness or granmotherlyness and wisdom comes first to keep up the deception of beloeved and trustworthy rulers
so Jeremey Kapone is the right casting for the role of Freddie Mercury, not a known for their own self and name
but to become known and believed in their acting the part of Freddie .