but it is Allah will that He can let some of it known to his selected Slaves.
He used Isa Alaihissalam for showing the cure of leprosy and blind but didnot give to many other Prophet.
He knows from the beginning, but He may let it know later to his Prophet or his friends (Aulia Allah)
A muslim believe that Karamat/ Kashf is totally under control of Allah.
It is not related to the will or status of a person (Prophet or Aulia Allah) .
It is by Allah will and not the Desire/status of person have much Role.
If these unusual/impossible things are manifested at the hand of Prophet it is called MAUJAZA.
if it is manifested Aulia Allah other than Prophet it is called Karamat.
Sometimes a person other than Prophet may get Kramat from Allah.
Eg: Quran says that Hazrat Mariyam used to get fruits without season and Prophet Zakaria was not getting,But it does not mean that she became bigger than Prophet.As already being said that through kashf a lot of things can be seen/feel with the permission of Allah.like this one:
KARAMAT/KASHF OF ABU BAKAR RAZIALLAHU ANHU
'A'ishah narrated: "When he(Abu bakr) was on his deathbed, my father(Abu bakr) said to me: "Verily, you have two brothers and two sisters." So, I became startled at this, as I only had two brothers and one sister. He referred to his then-pregnant wife, Bint Kharijah, saying: "I see that she is pregnant with a girl," and that turned out to be exactly the case."
[Reported by ash-Shatibi in 'al-Muwafaqat' (4/85), and Ibn Taymiyyah mentioned it in 'Majmu' al-Fatawa' (11/318)]
Yaqub Alaihissalam could not trace from the well of Kunan But By will of Allah he could smell the cloths of Yusuf Alaihissalam from far away Egypt.
So if you will see the Karamat e Aulia with Muslim vision you will find the greatness of Allah.
Otherwise you may find something else if you consider that it has been done by the Aulia Allah, then it will become shirk,as Some of the groups are smelling/making Propaganda of Shirk in Aulia Allah Stories.
SHAIKHUL ISLAM IBNE TAIMIYYA R.A. views on these Issues
"The miracles of saints are absolutely true and correct, by the acceptance of all Muslim scholars. And the Qur'an has pointed to it in different places, and the Hadith of the Prophet (s) has mentioned it, and whoever denies the miraculous power of saints are only people who are innovators and their followers." [al-Mukhtasar al-Fatawa, page 603].
Ibn Taymiyya says, "what is considered as a miracle for a saint is that sometimes the saint might hear something that others do not hear and they might see something that others do not see, while not in a sleeping state, but in a wakened state of vision. And he can know something that others cannot know, through revelation or inspiration." [Majmu'a Fatawi Ibn Taymiyya, Vol. 11, p. 314].