Regarding Martial, and take it with a grain of salt as it's from Reddit:
Anthony Martial was always a huge talent; he joined OL at the age of 14 and he was always recognized as basically the gem of his generation. at age 16 he scored 32 goals in 21 matches in the French U17 division and he was getting to play with the first team at age 17. Martial was often regarded as one of the best out of his group of NJie, Fékir, Benzia, Ghezzal, etc from OL's academy.
OL are a club that is floated on the stock market, so they have to maintain strong enough finances for their shareholders. OL were in a bit of financial difficulty at the end of the 2012-13 season and they needed to sell one more player in order to balance the accounts. naturally, eyes turned to Bafétimbi Gomis who had a decent season, but the club wanted to sell him before his contract expired in 2014.
Gomis was basically being pushed out by OL. there was interest from France, England, Germany, Italy, and even Turkey. the advisor Bernard Lecombe said himself that Monaco, Swansea, Leverkusen, Fiorentina and Fenerbahce were all interested in signing him. Gomis had already agreed in the past to not leave on a free...but then he changed his mind at the worst time possible.
as expected, there were major protests from fans about the transfer. Martial was the future for many years, and Gomis would have been gone after one more season. OL officially stated that the president Jean-Michel Aulas would meet with Gomis and Lacombe to find out a way to make Gomis more open to negotiating a move away from the club, but he wouldn't leave.
OL gave Gomis months, giving him a deadline of June 30 to make a decision. But at the last minute he pulled out of everything and Monaco swooped in for Martial. now imagine if OL still had Martial alongside Lacazette and Fékir, which would have been spectacular. if I could feel bad for OL, I would.
but alas, it was not meant to be. OL sold Martial for 5 million euros, with a significant profit on any future transfer and the solidarity fee. in the official statement, they even made a dig at Gomis for not leaving yet. and now a couple of years later, Martial is where he is at now, and Monaco could be selling him for 50+ million euros.
