Any notion that COVID-19 was going to last for just a few months was very much misplaced in 2020. Especially after it was recognised that the SARS-CoV-2 virus was largely spread through the airborne route, all indications were that it would cause repeat bouts of waves. This is what happened in the flu epidemic of 1918. Pasha 118: Herd immunity isn’t achievable. We need to learn to live with COVID-19. The Conversation Africa - Pasha, CC BY-NC-ND15.8 MB (download)
In addition very few scientists predicted that we would see the type of mutations that occurred over such a short period of time. This has resulted in the virus becoming both more transmissible and more able to evade immune responses.