Combination of sunk cost fallacy/bureaucratic inertia ("we've always focused on Russia as a threat, why should we change?") plus the fact that while the Russia hysteria is overblown insanity, there still are nonetheless many geopolitical issues with which the U.S. has serious differences with Russia. Primarily that Russia continues to be the main economic and military partner for nations that are hostile to us and our allies/interests such as Syria, Iran, and Venezuela. Russia of course will not cut these nations off because that would be a net negative for them both economically and diplomatically, and our own policy makers can't or at least shouldn't just hand-wave those nations receiving Russian military or economic aid as "lol, no biggie" because them becoming stronger while still being adversarial would not benefit us.
It's the simple, real-world result of two-major powers trying to project influence and protect their national interests - there's inevitably going to be places where they clash. That doesn't mean though that things need to necessarily reach the level of tension that the current crop of idiots have allowed things to escalate to, though.