I had a question that was doing very well & the number of views as well as likes was increasing fast, but I don't know why suddenly everything stopped & now it behaves as if it's a duplicate or closed post.Is there any reason? Such a sudden change seems really abnormal.
Actually your question is now at normal state. You were getting so much interaction before because your question became a hot network question and was also tweeted by the automated Ask Ubuntu twitter account. See the timeline of your question:
Enough time has passed that both of these are probably irrelevant now, hence the drop off in views.