Poch is not known for rebuilding and Chelsea needs someone that can manage potential.
Pochettino is a decent manager, but i think Julian Nagelsmann and Luis Enrique were better options, i still wonder why talks between the two of them and Chelsea fell through. Pochettino was manager of Spurs for quite sometime, and i wouldn't deny the fact that i love how he sets his team up to play, and that's in the offensive way, he doesn't sit back and absorb pressure nor park the bus.
Having said that, i don't think Pochettino can lead Chelsea to trophies, they will definitely bounce back to become a decent team, but they aren't going to compete for the EPL title as some people think, their goal next season should be to get themselves back into the CL and prolly win either the Carabao or FA Cup.