I would venture a guess that because stray dogs are/were such big problem in Russian cities, so it was hard to even pass legislation against killing them, as reported in Dec 2018:
Russia has banned petting zoos, animal cafes and the killing of stray dogs and cats under a new law submitted eight years ago that dramatically overhauls rules overseeing the treatment of domestic and wild animals.
Stray dogs roam the streets of many Russian cities and towns, and attacks by — and against — the animals have become increasingly frequent. Animal rights activists have called for humane control measures of stray dogs, as vigilantes around the country have shot or administered poison to kill the animals.
The new law — welcomed tepidly by animal welfare activists — bans animal fights, pet cafes and petting zoos that house exotic animals, often inside malls. Bars and restaurants are also banned from housing animals, while wild animals cannot be kept in apartments and private houses.
“This law covers only one percent of what we’d like to see,” Irina Novozhilova, head of the animal rights group Vita, told the RBC broadcaster. [...]
The law prohibits the killing of stray animals, requiring them to be captured — out of sight of children and recorded on cameras for public access — and placed in shelters instead.
Likewise Russia (or rather the USSR before it) had bit of a tradition with animal experimentation, including in space (Laika etc.) There has been a bit of political football somewhat recently (December 2017) over something like that as well:
Deputy PM Dmitry Rogozin was showing [Serbian] President Aleksandar Vucic the results of the latest Russian research into liquid breathing whereby, rather than breathing air, an organism breathes an oxygen-rich liquid.
As part of the demonstration, broadcast on St Petersburg's Channel 5, scientists in white coats put a dachshund named Nikolas headfirst into a container filled with the oxygen-saturated liquid. [...]
"The liquid gets into the lungs and the animal starts breathing in the liquid," a commentator told the guests.
Although the dog survived the experiment, social media users and animal rights activists were quick to accuse Mr Rogozin of cruelty to animals.
"A Russian deputy PM with colleagues are mistreating the poor dog. Mistreating humans isn't enough for them, they are not letting dogs live," a popular blogger, who is often critical of the Russian authorities, said in a widely-shared tweet. [...]
However, several pro-government TV channels supported the experiment.
There's a survey (albeit not of great quality) comparing public opinion in BRIC countries on such matters to that of the US. There isn't actually a lot of difference in that regard.
So differences seem mostly explained by political and legislative peculiarities rather than big differences in public attitudes.
But Russia did get low marks for animal protection laws in general (note that this was prior to the recently enacted legislation), e.g.:
In 2014 Russia's animal protection regulations received an F out of possible grades A,B,C,D,E,F,G on World Animal Protection's Animal Protection Index
For some (BRICS) contrast, China got an E, Brazil and India a C, and South Africa a D.
Another (2013) publication noted (regarding the same survey) that
A global review of animal protection legislation carried out by the World Society for the Protection of Animals
(WSPA) reveals that Russia lags behind many countries, having no legislation for fifteen of the sixteen areas
Also, formally recognizing animal sentience in law is somewhat of a new thing; the TFEU was amended for example in 2009 in this respect (by the Lisbon Treaty). And Russia has not been on very good terms with the EU since then, so appearing to copy western liberal ideas was probably not seen favorably domestically.