I don't think you can at all underestimate the draw of Venom as a character and the appeal fans saw in seeing him realised 'properly' on the screen for the first time. How many tickets sold can be attributed to that curiousity/fervor I dunno; I'm sure perceived MCU connections helped a great deal also.
But vocal audience reaction, reactions we all could see out there, was overall decidedly mixed so I don't see many other explanations for it's success other than there being a silent majority that ate it up in spite of what we know
Silly shit just sells, sometimes ¯\_(ツ)_/¯