True but but there's been a few teams there, squeaking 2nd is well in the top 4. Their aspirations may have changed over the years from trophies to top 4 but they have always met them. This year is the exception so it's understandable that people would of backed them to do the usual.
There was a club that played in Europe every season for twenty years from the mid sixties, winning 4 European Cups and 2 UEFA Cups. They went on another run once they got back into Europe, winning another European Cup and another UEFA Cup, topping the rankings as the best team in England...
And then they weren't the highest ranked team in England and they didn't qualify for the knock out phases and then they missed out on Europe completely.
People go on about Arsenal but until last year Chelsea had been in the Champions League for 13 straight seasons. The difference being that they've actually won it in that time as well as picking up a UEFA Cup under Rafa when they dropped out after the group stages. United have missed out on the CL a couple of times but again, they've actually won the thing.
A few year's back you;d have backed Liverpool, Chelsea and United to be in the Champions League every season. Arsenal getting top four has become a 'thing' because it's the only thing they do - it's their biggest trophy (along with the St Totteringham's Day Trophy and the Emirates Cup).