The steps that many people and countries took to reduce the spread of COVID reduced the spread of many other infectious diseases as well. As the precautions relaxed, infections grew.
I also think that, because so many people were infected, the mutation rates for these viruses were pretty slow, so that the viruses that spread right after COVID restrictions were relaxed were not highly mutated. Moreover, air travel continued to be limited for a while, so long-distance spreading of viruses was curtailed.
So, in all, people’s immune systems may be a bit “out of practice” at dealing with new mutations of the common cold and similar URTIs.