There are plenty of other contemporaneous sources all saying the same thing. Similar to the now dis-proven Russia-gate hoax, the DNC are the ones pushing the narrative that the leak was a Russian operation. The analysis of the time stamps on the DNC files has proven that they were not copied over a network, but copied locally.
CrowdStrike is a 40 billion dollar cyber security company. You must be deep down the conspiracy rabbit hole to be convinced it is a front for a think tank. Dmitri Alperovich is a well respected and experienced security professional.