Again, this isn't idle speculation: genuine mainstream health authorities believe lockdown has killed significant numbers of people. This is not a controversial position.
No, the question is why does the excess deaths distribution perfectly align with the expected and recorded COVID death spike and drop so sharply afterwards when lockdown was still in place.
It's uncontroversial that lockdown has killed and saved significant numbers of people for reasons other than COVID, but similarly it is entirely uncontroversial that the aggregate increase in excess deaths was caused by COVID. The idea that the inflection point COVID-time-to-death days after the start of lockdown is better explained by unannounced changes in policy or your personal advice to friends and family, on the other hand is about as scientifically credible as blaming 5G.
Sure, but we can look at when the excess deaths happened. Instead of being evenly distributed across the lockdown period, or peaking towards the end when people had longer without access to support, they came exactly when you'd expect deaths from an epidemic wave to peak before plummeting to normal levels towards the end of the lockdown period. Undoubtedly, individual deaths have resulted from lockdown, but the pattern of excess deaths matches COVID rather than lockdown being behind the aggregate increase.