Answer by taking a quote from the following article:

Sir Donald George Bradman, AC (27 August 1908 - 25 February 2001), often referred to as "The Don", was an Australian international cricketer, widely acknowledged as the greatest batsman of all time. Bradman's career Test batting average of 99.94 has been cited as the greatest achievement by any sportsman in any major sport. The story that the young Bradman practised alone with a cricket stump and a golf ball is part of Australian folklore. Bradman's meteoric rise from bush cricket to the Australian Test team took just over two years.

In 1930-31, against the first West Indian side to visit Australia, Bradman's scoring was more sedate than in England--although he did make 223 in 297 minutes in the Third Test at Brisbane and 152 in 154 minutes in the following Test at Melbourne. However, he scored quickly in a very successful sequence of innings against the South Africans in the Australian summer of 1931-32. For NSW against the tourists, he made 30, 135 and 219. In the Test matches, he scored 226 (277 minutes), 112 (155 minutes), 2 and 167 (183 minutes); his 299 not out in the Fourth Test, at Adelaide, set a new record for the highest score in a Test in Australia. Australia won nine of the ten Tests played over the two series.  At this point, Bradman had played 15 Test matches since the beginning of 1930, scoring 2,227 runs at an average of 131. He had played 18 innings, scoring 10 centuries, six of which had extended beyond 200. His overall scoring rate was 42 runs per hour, with 856 (or 38.5% of his tally) scored in boundaries. Significantly, he had not hit a six, which typified Bradman's attitude: if he hit the ball along the ground, then it could not be caught. During this phase of his career, his youth and natural fitness allowed him to adopt a "machine-like" approach to batting. The South African fast bowler Sandy Bell described bowling to him as, "heart-breaking ... with his sort of cynical grin, which rather reminds one of the Sphinx ... he never seems to perspire".  Between these two seasons, Bradman seriously contemplated playing professional cricket in England with the Lancashire League club Accrington, a move that, according to the rules of the day, would have ended his Test career. A consortium of three Sydney businesses offered an alternative. They devised a two-year contract whereby Bradman wrote for Associated Newspapers, broadcast on Radio 2UE and promoted the menswear retailing chain FJ Palmer and Son. However, the contract increased Bradman's dependence on his public profile, making it more difficult to maintain the privacy that he ardently desired.  Bradman's chaotic wedding to Jessie Menzies in April 1932 epitomised these new and unwelcome intrusions into his private life. The church "was under siege all throughout the day ... uninvited guests stood on chairs and pews to get a better view"; police erected barriers that were broken down and many of those invited could not get a seat. Just weeks later, Bradman joined a private team organised by Arthur Mailey to tour the United States and Canada. He travelled with his wife, and the couple treated the trip as a honeymoon. Playing 51 games in 75 days, Bradman scored 3,779 runs at 102.1, with 18 centuries. Although the standard of play was not high, the effects of the amount of cricket Bradman had played in the three previous years, together with the strains of his celebrity status, began to show on his return home.

Was he always considered a hero?
set a new record for the highest score in a Test in Australia. Australia won nine of the ten Tests played over the two series.