Czech language readily borrows, steals, modifies, and combines words from all around the world to create new words for itself. Slibotechna is one of those. It probably was created sometime between 1900 and 1980, and it has remained in the vocabulary ever since.
How can I be so sure about the timeline? Because the suffix “techna” is a derivative of the word “technologie”. And it was used since the start of the 20th century as a suffix for naming companies, where the prefix hinted somewhat at what the company makes. Like “Elektrotechna” (manufacturer of radios and similar) or “Mototechna” (manufacturer of cars and motorcycles). It was especially used in the 50s for naming newly established state monopolies.
And during that time, some smartass added the prefix “slibo” to this widely used suffix. “slibo” is a derivative of the word “slib”, which means “promise”. Thus, a new word was created for someone who constantly overpromises and underdelivers, or, even worse, just promises and never delivers.
Does English have a similar word? I think there is a need for one. I was reminded of the Czech one recently with Trump’s third promise of thousands-of-dollars cheques for US citizens.

We call it “vaporware”, but I feel sure multiple nuances of meaning differ between the two terms.
I expect it will eventually be Trumptechna worldwide.
Would that make Trump a “slibopolitik”?
@rsmith, slibotechna covers politicians already. But the portmanteau you created would be technically correct, although it does not roll off the tongue.