He is asking about the reason why the fatwa on photography was changed

In fact what you mentioned about the change in the fatwa on
photography may not be quite correct. We need to differentiate between two
matters when it comes to the matter of photography or image-making. 

The first matter is the ruling on photography or making
images of animate beings. This is the crux of the matter. What we are
referring to is two-dimensional pictures (as opposed to three-dimensional
images). 

The saheeh Sunnah indicates that these kinds of images are
haraam, whether they are on a poster, paper, garment or wall, because it is
imitating the creation of Allah. 

An-Nawawi (may Allah have mercy on him) said: 

Our companions and other scholars said that making images of
animate beings is emphatically forbidden and is a major sin, because of the
stern warning issued concerning it in many hadeeths. Regardless of whether
the final product is something that will be handled in a disrespectful
manner or otherwise, making them is haraam in all cases, because it is
trying to imitate  the creation of Allah, may He be exalted. That applies
whether the images are on a garment, carpet, a dirham, dinar or other coin,
a vessel, a wall, or anything else. 

With regard to making images of trees, camel-saddles and
other inanimate objects, that is not haraam. This is the ruling on the issue
of image-making. 

There is no differentiation in any of these matters between
that which has a shadow and that which does not have a shadow. 

This is the summary of our opinion concerning this matter,
and something similar was stated by the majority of scholars among the
Sahaabah, Taabi‘een and those who came after them; it is also the opinion of
ath-Thawri, Maalik, Abu Haneefah and others. 

Some of the early generation said that it is only that which
has a shadow that is forbidden, and there is nothing wrong with images that
do not have a shadow. But this is an invalid point of view, because no one
doubts that the curtain that the Prophet (blessings and peace of Allah be
upon him) objected to because of the images on it was something blameworthy,
and its images did not have a shadow. And we should also bear in mind all
the other hadeeths which speak in general terms about all images. Az-Zuhri
said: The prohibition applies to images in general.

End quote from Sharh Muslim by an-Nawawi, 14/81 

We have previously discussed the evidence for the prohibition
on image-making and some of the texts of the scholars concerning that in
many answers. See the answer to question no.
7222 

This is a matter concerning which we know of no fatwa that
has been changed, or that anyone who said that image-making is haraam
changed his mind and said that it is permissible, or that most muftis were
of the opinion that it was haraam but now they think it is permissible. Even
if we assume that some such change has taken place, it is very little or is
odd and rare, and cannot be taken into account. 

The second matter is: does the ruling on image-making apply
to specific types of images, such as photographs for example? If it does
include that, does this prohibition apply only to a complete image or does
it also apply to partial images? And there are other such issues concerning
which the faqeehs and muftis differed as to whether the ruling mentioned
above is applicable to these modern forms of image-making. 

This is a matter concerning which there is a considerable and
well known difference of opinion among the scholars. Some are of the view
that photographs come under the heading of image-making that is haraam,
because it is a kind of image-making and because what is produced by means
of it is an image, so it comes under the ruling on images of which the text
speaks. 

Some scholars are of the view that the reason for the
prohibition on image-making, which is imitating the creation of Allah, is
not applicable in the case of photography, because it is merely capturing
the reflection of a person, so it is permissible and is like looking in a
mirror and the like. 

This is not the place to discuss that; rather the aim is to
point out that there is a difference between saying that there are
differences concerning the ruling and saying that there are differences
concerning the application of the ruling in specific cases. 

We have discussed the ruling on photography in many answers
on this site. Please see the answer the questions no.
13633,
10668, and
7918 

As this is the case, there is nothing strange about a scholar
or mufti having different views concerning new developments. He may have
based his ijtihaad at some time on the assumption that the photograph would
have to be processed by a human in some way, which is the same as the work
of the image-maker, so for that reason he ruled that it is haraam; then
things may have changed and equipment may have been developed, so there is
no longer any need for human involvement. 

In fact we may say, to further clarify this point, that the
view of a scholar may change from one time to another on the same issue, and
this is nothing new; rather it is something that is well known and well
established. The fact that there are two Shaafa‘i madhhabs, old and new,
bears witness to that. And the differing reports from Imam Ahmad and others
on a single issue are well known. 

The examples of that are very well known, and the matter is
not to be established on the basis of what this one or that one said; rather
what matters what evidence there is to prove a given view. 

We ask Allah to help us all to do that which He loves and
which pleases Him. 

And Allah knows best.