I remember elections in many troubled countries, but I don’t remember the American media ever referring to them as a “sham”. Even in Zimbabwe, Iraq and Libia, they never disparaged the democratic process.
I can only conclude it’s because their favored side is going to lose.
Pew and other recognizes pollsters do not poll Crimeans and East Ukrainians much. You know why.
Your memory is about as reliable as a Russian referendum. Here's a 2013 article referring to Robert Mugabe's 2013 election in Zimbabwe as a "sham".
https://www.cfr.org/blog/zimbabwe-elections-sham
Here's an article referring to the 2002 Iraqi referendum that gave Saddam another 7 year term as a "farce".
http://news.bbc.co.uk/2/hi/2331951.stm
And Ghaddafi was never actually elected to anything.