Not to be condescending, but because people have been saying for a year now or more now that the virus will rapidly evolve and any vaccines will become less effective over time because of it.
And the virus rapidly evolved and the vaccines we have became less effective to new strains, as expected. A quick deployment of vaccines would greatly reduce that risk (see: Japan currently having infections in the double digits following a rapid deployment in vaccines and universal masks, leaving little room for new strains to adapt).
The pandemic has been a long chain of some insightful people saying "This bad thing will happen if people don't take X precaution." People say that's a lie--then don't take X precautions. Bad thing happens. People get angry and say they were lied to because bad thing happened when they were told it wouldn't happen (because loads of people took no precautions). Then there's a warning about another bad thing happening, followed by denial.
And the virus rapidly evolved and the vaccines we have became less effective to new strains, as expected. A quick deployment of vaccines would greatly reduce that risk (see: Japan currently having infections in the double digits following a rapid deployment in vaccines and universal masks, leaving little room for new strains to adapt).
The pandemic has been a long chain of some insightful people saying "This bad thing will happen if people don't take X precaution." People say that's a lie--then don't take X precautions. Bad thing happens. People get angry and say they were lied to because bad thing happened when they were told it wouldn't happen (because loads of people took no precautions). Then there's a warning about another bad thing happening, followed by denial.