Sometimes ago I found an article which devotees were unable to draw a conclusion as to how it can happen. How can Krsna and Balarama jump 88 miles
from mountain and where is the mountain?
VERY easy explanation: Krsna is the SUPREME PERSONALITY OF GODHEAD - He can do WHATEVER He likes. When He descends in the material world the WHOLE Vaikuntha descends with Him - so He brings all the MYSTICAL powers which seem bewildering to common man. Krsna is yatra yogesvarah krsno(Krsna, the master of all mystics)
This is WHY Krsna is God - omnipotency - all powerful. He can DO IT common man can not. Even yogis have mystic powers BUT Krsna is the ORIGIN of mystic power.
Anyway, lets look at a few understandings:
KB 52 Krsna, the Ranacora
After traversing a very long distance, the brothers pretended to become very tired. To mitigate Their weariness They climbed up a very high mountain several miles above sea level. This mountain was called Pravarsana due to constant rain. The peak was always covered with clouds sent by Indra. Jarasandha took it for granted that the two brothers were afraid of his military power and had hidden Themselves at the top of the mountain. First he tried to find Them, searching for a long time, but when he failed he decided to trap and kill Them by setting fires around the peak. He therefore surrounded the peak with oil and set it on fire. As the blaze spread more and more, Krsna and Balarama jumped from the top of the mountain down to the ground--a distance of eighty-eight miles.
Bg 18.78 Conclusion--The Perfection of Renunciation
yatra yogesvarah krsno
yatra partho dhanur-dharah
tatra srir vijayo bhutir
dhruva nitir matir mama
Wherever there is Krsna, the master of all mystics, and wherever there is Arjuna, the supreme archer, there will also certainly be opulence, victory, extraordinary power, and morality. That is my opinion.
Note: even Krsna's devotees are POWERFUL.
SB 5.1.30 P The Activities of Maharaja Priyavrata
There is a Bengali saying which describes that someone is so powerful that he can make the night day and the day night. That saying is current because of the prowess of Priyavrata. His activities demonstrate how powerful he became by worshiping the Supreme Personality of Godhead. Lord Krsna is known as Yogesvara, the master of all mystic powers. In Bhagavad-gita (18.78) it is said wherever there is the master of all mystic powers (yatra yogesvarah krsnah), victory, fortune and all other opulences are present.
The other issue is trees, humans etc REDUCED in size in KALI-yuga so this means in other ages they were considerable hight.
KB 52 Krsna, the Ranacora
When Mucukunda, the celebrated descendant of the Iksvaku dynasty, was favored by Lord Krsna, he circumambulated the Lord within the cave and then came out. On coming out of the cave, Mucukunda saw that the stature of the human species had surprisingly been reduced to pygmy size. Similarly, the trees had also far reduced in size, and Mucukunda could immediately understand that the current age was Kali-yuga.