For Your Kind Information ->>
1. Instagram Has Changed #followed_by
To #edge_followed_by
(source: view-source:https://www.instagram.com/cristiano), This Is One Of The Reasons Why It Is Returning 0.
2. Add "?__a=1" To Insta Profile Url (https://www.instagram.com/cristiano/?__a=1) And You Will Get Json, Just Decode Json And Get The Value.
3. These Are Not Legal Ways To Get Information From Instagram. I Prefer To Use Instagram API, Which Is Easy To Use And Free.
UPDATE
4. Or You Can Get Followers From <meta>
Tags Instead Of <script>
Tags (Example - <meta content="310m Followers, 476 Following, 3,095 Posts - See Instagram photos and videos from Cristiano Ronaldo (@cristiano)" name="description" />
)