Why? Think of it for a moment. Five is an omnipresent theme in nature. Fruit, flowers, stars, hands, toes... even your own body is essentially a "five." (No, don't be silly, I don't mean five out of ten. :) I mean it has five main branches.)
This blows my mind because before we were even thought of, before the first human had gone astray and sentenced the Savior to die to redeem our race, God had scattered the image of His own crucifixion across the earth and the heavens.
Is this morbid? Some would say so. But in fact it is quite the opposite.
But the Lord was pleased
To crush Him, putting Him to grief;
If He would render Himself as a guilt offering,
He will see His offspring,
He will prolong His days,
And the good pleasure of the Lord will prosper in His hand.
Isaiah 53:10
God was pleased to crush His own priceless Son. Not in the relatively shallow sense we tend to think of pleased, but a deep, complex, overflowing joy and satisfaction at this holy act of obedience which would change heaven and earth forever.
Jesus, You are the Father's incomparable, fragrant, impeccable Rose.