Because people live vicariously through both artists and think one person's success = their success and end up taking it way more seriously than it actually is. It's validation seeking, they can't just look at things and go, "it's not for me personally, but I respect your opinion and tastes." They don't like the music unless everybody else likes it, then they're all over it, and that's strange. It's numbers this, critical reception that, and none of it ever seems to be based on what actually matters -- the quality of the music. The metrics are fun to talk about, but if numbers and critics were all that mattered, then Taylor Swift is killing almost everybody out here.
Of course Drake is going to do high numbers, because he's Drake. The expectations are there, and he's had a pretty normal album roll-out. On top of that, he hasn't largely pissed people off between the release of Scorpion and now, and the beef he has with Kanye is inevitably going to make people curious about what he's gonna say on there. It also helps that CLB isn't a bad album either. It's not a classic, but it has all the typical tropes of what you'd expect from a Drake album. And if that's what you love about his music, it's all there, even if he's walking on familiar ground for most of it. Which isn't necessarily a bad thing either, if done correctly. Whether you feel it was or not is up to the listener's opinion.