M4 armor is crap
Nonsense. Its armor was comparable to the later Panzer IVs with a superior slope, and thicker than the T-34/76s but with less slope.
that's one of the reason its call the ronson.
Incorrect. The reason it got nicknames like "Ronson" and "Tommy Cooker" was because of a deficiency in its ammo stowage, not its armor, making it more likely to go up in a blaze
when penetrated than other contemporary medium tanks. This deficiency was remedied in the "w" models, which include both the new Shermans, by "wet stowage" of ammo which made the risk of fire more comparable to other tanks.
Except the french
Incorrect. Almost all of the French tanks deployed in 1940 had heavier armor than their German counterparts. The French stopped building tanks (as opposed to various specialty vehicles built for the Germans) after 1940, so their armor didn't get scaled up like the Germans' did, but there were still a few 1940-vintage German Mk. IVs soldiering on in Normandy in 1944, and they still had thinner armor than the
Char B and much thinner than any M4.
the Sherman had the thinnest armor in the war
Adressed above. There were scads and scads of tanks in the war with thinner armor, many of them still operating in 1944 - for starters, every Japanese tank employed anywhere outside China or Japan and every Italian tank employed anywhere (apart from about 100 non-turreted TDs). Tigers get all the attention but they were much rarer in RL than in the game; Germany produced in the ballpark of 20,000 medium tanks plus many thousands of light tanks, TDs, SPs, and other ACVs, and the only tanks (as oppose to TDs) out of all those that had armor substantially superior to the Sherman were about 6,000 Panthers.
(Also, anecdotal accounts from Allied soldiers make the Tiger seem more common than it was since inexperienced troops generally looked at anything heavier than a 38(t) and saw a Tiger.)
only reason it was successful was the numbers it was produced.
As successful as it was, sure, but then it was arguably more successful than any other tank in the war aside from the T-34 which was produced - and lost - in even greater numbers. Anyway they did well enough when not overmatched against Panthers or Tigers, at 2nd El Alamein, for example. And the early problems were more due to green US troops facing Rommel's seasoned veterans, at Kasserine for example - the US could have had Pershings or even Panthers and the outcome would have been the same when they rolled obliviously right up to well-concealed 88s.
Also, as Stalin said, quantity has a quality all its own.

However powerful the Tiger was, it was a bad design because it was moredifficult to produce than it was worth on the battlefield: maybe the Allies needed 5 Shermans or T-34s to kill a Tiger or Panther, but given that they produced
twenty times as many that was only a problem if you were a Sherman or T-34 crewman. And add to that something that the game regrettably (and IMO mistakenly) doesn't address, mechanical reliability, and the Allied tanks come out that much better in the balance.