It isn't, but it does massively help.
While Bayonetta did not originate from a Nintendo console, its sequel and survival as a series can be owed to Nintendo paying for its production in exchange for exclusive rights to publish the game on its console. This can be seen in how Bayonetta 3 is going to be a Switch exclusive as well. So while initially, Bayonetta's multiplatform, the series is now inextricably tied to Nintendo.
Cloud, while he himself has never appeared in a main game on a Nintendo console represents Final Fantasy as whole which has had six hugely popular games tied to a Nintendo console. Not as popular as FF7 granted, but honestly, what is?