West Ham United started well in the early minutes of the game but the goal they scored was supposed to weaken Chelsea but it motivated Chelsea to come back stronger and attack West Ham United to the point of making the west Ham United players especially their defenders very confused and unable to withstand their attacking force. Against Sunderland West Ham United had a better opportunity of not losing the game because their squad depth is a good match to Sunderland but they allowed Sunderland to overpower them and they lost also. Losing against Chelsea wasn't surprising but the number of goals they lost with shows that they aren't going to have a good season.
Yes, you are right. The goal that was supposed to weaken Chelsea actually weakened West Ham.
West Ham thought they could hold on for the whole match after scoring. But they didn't understand the strength of the opposing team's attack. In a crucial match, West Ham took Chelsea lightly and helped them to the top of the points table. The lack of coordination we saw in West Ham's midfield and defense was very painful. But Chelsea took advantage of every mistake their opponent made.
If Chelsea plays with this kind of strategy, they can take home the trophy this time.