This part is not really true.
The team that won 4 CLs in 5 years was:
Casillas/Navas
Ramos
Varane/Pepe
Marcelo
Carvajal
Modric
Kroos/Alonso
Casemiro/Di Maria
Ronaldo
Benzema
Bale/Isco
Casillas, Ramos, Pepe, Marcelo, Ronaldo, Alonso, and Benzema were at the club before Mourinho. He tried to replace Casillas with Lopez (who was worse) and tried to replace Marcelo with Coentrao. Carvajal, Kroos, Bale, Navas, and Isco all came in after Mourinho. Casemiro came in six months before he left and played in Castilla, not with the first team. That leaves Modric, who arrived in Mourinho's last season and who he never used particularly well, Varane, who is widely known to be a Zidane-recommended signing, and Di Maria, who left the club one season after Mourinho.
He formed a good, competitive team, but it was largely scrapped and rebuilt to begin a new period of domination. His signings like Ozil, Khedira, Di Maria, Coentrao, Carvalho, etc. didn't last long at the club after he left.