If not for several things happening simultaneously, the game wouldn’t have been on a Friday night:

1) New Years Day was on a Thursday
2) The consensus undefeated #1 and #2 teams were independents and thus not obligated to one of the “then” four NYD “major” bowls.
3) Unlike the prior year when both teams were also undefeated, neither team had committed to one of the four major bowls before the final reg season polls came out. So they were both free-agents.
4) The Fiesta Bowl - which for years was a 2nd tier Jan 1 lead-in on NBC to the Rose Bowl - was looking to expand it’s prestige and move to being the 5th major bowl, so bidding with both teams for a de facto MNC game was a no-brainer.
5) The Orange and Sugar Bowls had locked in NYD night slots so it benefited nobody to split the night-time audience three ways. And a nooner de facto MNC game was a non-starter.

So through a combination of these 5 mostly coincidental events, the de facto MNC game ended up on a Friday night. But if by chance just one of these 5 circumstances hadn’t occurred, it wouldn’t have happened.