Steinitz was the first chess professional
Well, Atos, there were, for example, Greco, Philidor, Deschapelles, Bourdonnais, Schlumberger, Staunton, Kieseritsky, Harrwitz- all of whom made either a substantial amount of their income, or all their income for a period of time, from chess. I would call them all chess professionals.
I haven't had time to research this exhaustively, but while it is true that some of these made some income, some of the time, from chess-related activities, I would question the designation of professionals. Kieseritsky died a pauper so if he was a chess professional it really wasn't a great financial success. La Bourdonnais "died penniless in London in 1840, having been forced to sell all of his possessions, including his clothes, to satisfy his creditors." In what sense can we talk about people who were not sure where their next meal was coming from as professionals ?
Staunton did make some income from chess but he was also engaged in literary studies, which he gave as one of his reasons for not wishing to play Morphy at that particular time. (He was contracted to publish a work on Shakespeare in the same time-frame.)
Greco was allegedly described by Botvinnik as "the first chess professional" but Botvinnik was not a 'professional' historian. From what little is known about Greco, he seems to have made an income by teaching chess to aristocratic families rather than by playing as such. Also, of course, Greco and Philidor were not Morphy's contemporaries, the period we were discussing was the mid-19th century.
Take the past champions, time machine them here, take some DNA, clone them, kill the original, and let baby Morphy study chess form age 5 in the 21st century and of course he'd be GM strength... no one doubts that and it's not very interesting to talk about either... too much fiction in the setup and the conclusion is obvious (at least IMO).
People like to quote Fischer, but (again IMO) his quotes have to be taken in context as he was a very un-objective/biased individual. His chess was great, but his reasoning and thoughts were not so good. Not just political or anything like that... just day to day stuff, he's not someone whose quotes on any subject other than a chess variation I put much stock into.