The thing is that in Bulgaria current "pro-EU" politicians (think Borisov and Peevski) are so directly dependent on Putin, that anyone who is just friendly with him looks already better. I know it is a superficial observation, but this is the vote of superficial people. As a president, Radev had plenty of opportunities to substantiate his anti-corruption rethoric, and he missed them. It makes little difference whether he did it out of bad intention or inability (which is often claimed, but hard to confirm).