The first few months and fixtures following a FIFA World Cup often bring sweeping change—particularly when things didn't go to plan during the summer tournament.
Failures are dissected and assessed, with federations across the globe attempting to pinpoint why things went wrong, what fixes can be put in place, or whether simply chucking things on the scrapheap and starting anew is the best possible strategy.
The amount of upheaval depends on how poorly things went, as front offices feel the pressure to make a statement appropriate to the level of performance. For example, you would expect Germany to embark upon some serious introspection following a group-stage exit in Russia, while perhaps Brazil might only need a few minor tweaks given they were only beaten by a marvellous Belgium team.