And according to Wiki he did it in a sleazy, underhanded way.
From Wiki:
"Modell took control of Cleveland Municipal Stadium in 1973, which had been owned by the City of Cleveland but had become too expensive for the city to operate or maintain. He worked out a deal with the city whereby his newly formed entity, dubbed Stadium Corp., would rent the stadium from the City for $1 per year, assume all operating and repair costs and would sublease the stadium to its two primary tenants, the Browns and the Cleveland Indians, Cleveland's franchise in the American League of Major League Baseball.
The Indians organization became dissatisfied with Modell's Stadium Corp. as its landlord. Modell did not share the loge revenues earned from baseball games with the Indians. Also, rock concerts damaged the stadium playing field during baseball season, and Modell refused to improve the clubhouse. The Indians attributed to this their inability to attract high-quality free-agent players. Eventually the Indians persuaded City of Cleveland and Cuyahoga County voters to fund a new ballpark (which became known as Jacobs Field), by imposition of new taxes.
In turn, Modell was dissatisfied with the Indians' new ballpark because Stadium Corp.'s suite rental revenue decreased once Jacobs Field opened. Many suite customers switched their business from Cleveland Stadium's older suites to Jacobs Field's newer suites, due to the Indians' newfound success and popularity in the mid 1990s and because Modell's Stadium Corp. refused to decrease the annual rent for the suites even though the events for which the suites could be used decreased substantially (81 home games) with the loss of the Indians as a tenant.
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Modell declined to become a tenant in Cleveland's new Gateway Sports and Entertainment Complex, instead asking for improvements to Municipal Stadium. Because Modell's Stadium Corp. still controlled Municipal Stadium, it may have made more business sense for Modell to try to keep the Indians at Municipal, particularly as the baseball team began to show signs of improvement both on the playing field and at the box office. (The Indians went on to play in the World Series in 1995 and 1997, and sold out 455 straight games at Jacobs Field from 1995 until 2001.) The City of Cleveland agreed to make the improvements to Municipal Stadium which were to be funded through an extension of the sin tax, which was used to provide funding for the Gateway Sports and Entertainment Complex.
While the City of Cleveland, Ohio agreed to improve Municipal Stadium, Modell issued a public moratorium on discussions relating to the stadium issue or the future of his franchise.
It was during this time that Modell entered into secret discussions with the State of Maryland to move the franchise to Baltimore for the 1996 season. The announcement of the move occurred several days before the public referendum on the extension of the sin tax that would fund the improvements on Municipal Stadium as Modell had originally requested. Some say that the timing of the announcement was to cause the referendum to go down in defeat and thus allow Modell to make the case that he was not receiving the public support he needed to remain viable in Cleveland. The referendum was passed by a wide margin. He was assisted in the move by Alfred Lerner, who would go on to become the new owner of the reactivated Cleveland Browns franchise in 1998. Modell's move returned the NFL to Baltimore for the first time since the Colts left for Indianapolis after the 1983 season.
The reaction in Cleveland was, not surprisingly, very hostile.
Modell had promised numerous times never to move the team. The Brooklyn native mentioned numerous times how saddened and betrayed he and other Brooklynites had felt when the Dodgers moved to Los Angeles in 1957, he had publicly criticized the Baltimore Colts move to Indianapolis and he had testified in favor of the NFL in court cases where the league unsuccessfully tried to stop Al Davis from moving the Oakland Raiders from Oakland to Los Angeles.THE SLIME CONTINUES:
http://en.wikipedia.org/wiki/Art_Modell