Looking back at PSG's early Qatar days with Ancelotti
It might be difficult for younger generations of football fans to look back at a time when Paris Saint-Germain wasn't owned by the Qatari and wasn't the dominant force in French football. However, that was the reality of the club before 2011 and once they bought the club, it was the beginning of a whole new era, which included infinite monetary resources and a lot of high-profile signings.
The context
Paris Saint-Germain always had decent fortunes as a football club and were usually regarded as one of the most-known in France for a long time, having enjoyed several players such as Ronaldinho, George Weah, and Jay Jay Okocha. However, things took a turn for the unexpected when it was announced in 2011 that Qatar Sports Investments (QSI) purchased the institution, turning it into one of the richest clubs in the entire world and, by far, the richest in France.Club president Nasser Al-Khelaifi made it immediately clear that they wanted to bring the UEFA Champions League trophy to Paris and one of their earliest decisions to achieve that was to hire the Brazilian Leonardo as the clubs's Sporting Director. A club legend during his playing days, Leonardo oversaw the revamping process of the squad in the summer of 2011, signing the likes of Blaise Matuidi, Salvatore Sirigu, Maxwell, Kevin Gameiro and Javier Pastore, thus raising the quality of the team.
By December of 2011, while PSG had been eliminated in the UEFA Europa League and Coupe de la Ligue, they were at the top of the Ligue 1 table, with three points over Montpellier. However, the club chose to sack manager Antoine Kombouaré, leading to the hiring of Carlo Ancelotti, who has a good friendship with Leonardo.

The ups and downs with the club
It is important to point out here that Ancelotti wasn't brought to the club just to coach the team and win titles. He was hired to help instill the knowledge of how to run a world-class football team, especially because of his connection with Leonardo. It was revealed in the Italian's biography, Quiet Leadership, that the board at PSG didn't even know that the club needed to have a dining facility, which goes to show the context of the situation when he arrived to Paris.Therefore, Ancelotti had to deal with a club that was far from being perfectly suited at the time to compete at the highest level. However, he made do with what he had and pushed on with the team, to the point that his first defeat came several months after his appointment. That didn't stop the disappointment since Paris Saint-Germain would end up losing the 2011/12 Ligue 1 title to Montpellier with Olivier Giroud in the team, which is something that was a major blow at the time when considering the massive difference in resources.
While losing the league title was certainly a disappointment, Paris Saint-Germain's financial resources and Ancelotti's name would allow attracting major talents, and they did come. Signing players such as Zlatan Ibrahimovic, Thiago Silva, Ezequiel Lavezzi, Marco Verratti, and Lucas Moura would propel PSG to dominance of French football, winning the league in the 2012/13 with a lot of ease.
Naturally, though, the club's main ambition was the UEFA Champions League and their biggest ordeal until that point took place in the quarterfinals, going up against a prime Lionel Messi's FC Barcelona. While the Parisians didn't lose in both legs, with two draws (2-2 and 1-1), they would end up eliminated because of the away goal rule that was in place at that time.
This was naturally another heavy blow, but Ancelotti mentioned how proud he was of the team and, having won a league, it seems that the club was on the right path to the coveted Champions League trophy. It wouldn't be with Ancelotti who would lead them to that though, since he requested to leave so he could join Real Madrid in the summer of 2013.
Conclusion
Carlo Ancelotti's time at Paris Saint-Germain might be regarded as a footnote in the career of the Italian manager, especially considering the tremendous amount of success he have had in huge clubs such as AC Milan and Real Madrid. However, he was part of the Parisian club at a time when they were making their transition to become a monumental force in French and European football, and there is an argument to be made that his influence was pivotal in that regard.Moreover, it is interesting to point out how his presence, as per what was stated in his book Quiet Leadership, helped provide a greater understanding to the board and the people at the club of how a top-class football club has to be run. It is something that is not often mentioned with managers and it is a factor that makes his time with PSG a lot more important in the grand scheme of things.
It was a somewhat peculiar moment for both parties, but one that would end up serving as a before and after mark in the history of French football as a whole.