The two cases you mentioned were very specific:
Evernham sold controlling interest to an idiot. Not only that but it isn't like the team itself is actually dead- RPM is more Evernham than Petty Enterprises, they just went with the Petty name because Evernham got out and Gillett was chased out of town.
DEI died because it was ran by a power hungry b**** who I can and will argue was and is losing grip on reality. Letting Dale Earnhardt Jr. walk away instead of allowing himself and his sister take over and preserve their father's legacy for no reason that I am currently aware of outside of "He parties too much" (Not that Budweiser didn't play a part in molding that image) is definite and irrefutable proof of this. Not only that, but merging with a guy as respected and legendary in motorsports as Chip Ganassi, only to eventually pretend himself and the team don't exist to the point where Ganassi takes the Earnhardt name off the side of the building shows irresponsibility and stupidity. Now, 13 years after her husband left this Earth unexpectedly, all she has done since is ruin everything he worked for and put into DEI, while trying to hawk all matter of merchandise and endorsement deals in the name of his "legacy". It's sickening.