Ericsson no longer makes phones. They're a highly profitable company building cell phone networks with lots of patents in the wireless tech-sphere. Samsung and Ericsson are not, in other words, direct competitors and this is not a case of competing through the courts. Key part from TFA:
"The suits were filed because Ericsson said it could not reach a license agreement for its patents with Samsung on fair, reasonable and non-discriminatory (FRAND) terms after two years of negotiations. Samsung was asked to pay the same rate as its competitors, but Samsung refused, according to Ericsson.
"Samsung had licensed Ericsson patents before. However, according to a statement released by Samsung last week, Ericsson demanded 'significantly higher royalty rates for the same patent portfolio,' adding that it planned to 'take all necessary legal measures to protect against Ericsson's excessive claims.'"
This is purely about the money. The two companies stopped negotiating, Samsung is betting that going to court (they must have known a lawsuit was coming) will end up better for them than paying Ericsson's fee.