The Bundesliga champions came from behind to claim a 3-1 win in the UEFA Champions League quarter-final second leg, completing a 4-2 victory on aggregate.
Guardiola said his side deserved their spot in the semi-finals, hailing them for proving too good for a defensive United outfit.
"It's not easy to play against eight players in the box, that happened in Manchester too, and we decided to try to create a little bit of passing in the middle," the Spaniard said.
"Quickly going to the (likes of) Arjen Robben and Franck Ribery and create the crosses. Manchester defend, Chelsea defend well, Arsenal defend well, the flankers, the crosses.
"At the end after 1-1, we played much, much better and deserved naturally to be in the semi-finals."
Patrice Evra's stunning 57th-minute opener gave United a shock lead, but Bayern hit back almost immediately through Croatian striker Mario Mandzukic.
Guardiola said he had no time to adjust his tactics in between Evra's opener and Mandzukic's opener, and Thomas Muller and Arjen Robben finished off the tie.
The former Barcelona coach said all the other semi-finalists – Real Madrid, Atletico Madrid and Chelsea – had plenty of quality.
"Every team has its qualities," Guardiola said.
"Real Madrid has an outstanding team, a lot of great players and they also have a lot of ball possession with (Xabi) Alonso, (Luka) Modric and so on.
"Atletico Madrid have such passion. They are in this situation for the first time. The fans they have and how they support them at the moment, it's unbelievable. It wouldn't be easy to play against them.
"And Chelsea is an English team with a lot of experience - with (Petr) Cech, (Branislav) Ivanovic, (John) Terry and (Frank) Lampard, plus they have a coach (Jose Mourinho) with a lot of experience as well."
