Would it be fair to say that defensive oriented managers lose it faster/more dramatically than offensive oriented managers? Seems like the second group have a better track record of staying relevant until retirement.
No they don't.
If you are example of offensive managers are only Guardiola and Klopp, yes.
However those aren't the only offensive managers out there, there are many offensive managers who have failed when they changed clubs like Marco Rose, Peter Bosz, Emery, Sampaoli, Sarri, Spaletti, etc
LVG is also an offensive manager, and his career at club level ended pretty bad at United, Wenger is another example of offensive manager ended his career in a very underwhelming way.
Mourinho has imploded, but Lippi and Capello knew when to retire from club football, and moved to international Football in the right moment.
Mourinho has been a failure since he left Chelsea in 2015...7 years ago.
That's not taking in account that Conte and Allegri are still doing OK, unlike Mourinho.
You are cherry picking Guardiola,Heyckens and Klopp as representation of average offensive managers, but they aren't.
Regardless of football philosophy, most managers are meant to fail, only a few can claim to be the best.