I'm not a fan of the Russian government, but let's stick to the facts. The biggest reason why the democrats lost is because they didn't give most people a reason to care to vote, they didn't listen to their more popular base on things like healthcare and a certain genocide as that could push away their corporate donors, and they promised continuity with an impopular administration that had the bad luck of governing during most of the economic hardship of the pandemic. Still, they could have done a decent campaign and ran on more popular policy.
Obviously powerful countries do try to influence elections to a degree, but the idea that Trump only won because of Russian interference has been disproven already.