For starters, there is no united group known as "liberals" whom either of us can speak on behalf of, but I will indulge you and also speak in generalizations.
Liberals do not arbitrarily support "moving as much power to Washington as possible". Rather, they believe strongly that human rights should be dispensed equally to everyone in the country. If abortion is a right, then being born in Texas shouldn't deprive a woman of that right any more than being born in the south in the 19th century should've deprived blacks of their freedom. Similar arguments can be made for gay marriage, miscegenation laws, female suffrage, the availability of healthcare for the poor, quality education, etc.
There's nothing whatsoever baked into the liberal ideology that supports things like domestic spying and warrantless wiretaps. Rather, the better explanation is any branch of government (in this case the executive branch) is incentivized to increase its own power, and people tend to be biased in favor of their party's presidents. But I've met countless pro-Snowden liberals, and I think you've really mischaracterized the essence of what makes liberals liberal.