First off, President Trump did not lose the election. That is a false premise to begin with. He won it fair and square and the democRATS stole it from him through massive election fraud in the battleground states by cheating. There's a difference.
And secondly, for the sake of argument, if President Trump did "lose" because of his "weak" pandemic response, why did Biden plagiarize Trump's response almost exactly, with the exception of adding more federal bureaucracy tasked with accomplishing the very same work as Trump's Coronavirus Task Force did? In other words, he did the same thing Trump did.
More biased, fake news from the Washington Compost, where we have learned to expect nothing better.
The uncontested narrative on most media outlets was that Trump was doing nothing but Biden had a plan. Biden dominated and controlled the narrative - without response - to most Americans. They strategically placed ads nationally on many networks that had no other political ads, allowing their message to air with low saturation from other similar ads. They targeted those who vote the most. That has an impact.