Both parties share the blame. With Trump some claim that it was Kamala's focus on trans that made the difference while others claim that she didn't focus that much on it if at all. My take is that both parties jump at the opportunity to focus on these lesser issues rather big picture items such as taxes, universal healthcare or anything else that would actually make a large impact in people's lives.
This is nothing new. I remember when Bernie was drowned out years ago and the focus became gay marriage instead of the much more important issues he was advocating for. The blame for focusing on these issues cannot fall just on the republican party. The democrats were more than happy to focus on these issues instead of something that might pit them against those that fund them. If all that matters is who is paying you behind closed walls, then it doesn't matter which party is in power at all.