Not really. Not everyone is affected in the same way. Lots of people continued to be paid as normal during the covid years, lots of people got more in support payments than they could have earned working normally. Likewise, over 3 million were excluded from covid support. So some winners and some losers. Lots of people are sitting on decent amounts of income or savings, whereas also lots of people are in massive debt and don't know where their next meal is coming from. Economic peaks & troughs have never affected everyone in equal measure, there are always winners and losers.
As for 20 million passengers flying out of London. Lots of the same people are counted multiple times. It's not 20 million "unique" individuals. So a single person may have been counted dozens or hundreds of times, i.e. if they work abroad and "commute" a couple of days per week, or if they're in a "sociable" crowd and jet off every few weeks for a weekend stag/hen do in Magaluf, or richer people jetting to Paris every weekend for a show and a meal or shopping.
I wouldn't be surprised if the 20 million actually turns out to be something like 5 million (or less) individuals, many of whom do multiple flights on a regular basis! At the same time, there'll be people who used to fly for holidays who now can't afford them (or simply want to avoid the airport chaos/stress).