2. Mike Williams is not good enough to be a WR1
This might sound controversial but this explains his inconsistencies more than anything. Mike Williams has not been as impactful since the start of the season because the start of the season was an anomaly. It is the one period of his career that stands out above the rest and for a reason.
Williams is a fine wide receiver don't get me wrong but he is never going to be worthy of being a WR1 on a good football team. However, because of his insane start to the season that will lead to decent numbers (also because the Chargers throw the ball so much), there will be a team that wants to pay Williams like a WR1 and that simply is not worth it.
Williams has ranked among the worst in the league in getting open against man coverage all season. That is a problem. A receiver cannot be a true WR1 if he cannot get open against man coverage and that has been the problem with Williams since the start of the season. Teams have noticed his flaws and have been able to man him up without having to pay for it.
Think back to some of Williams' biggest moments as well. A lot of his huge gains this season (which account for most of his receiving yards) were the result of broken coverage that left him wide-open. It was not elite route-running like Keenan Allen. It was defensive mistakes.
This also leads us to his best season as a pro thus far, 2019. In 2019, Williams hit the 1,000-yard mark because Philip Rivers decided to chuck balls up on a bad Chargers team without any real remorse. While Williams made some spectacular catches, it is not like he was open often. Rivers was throwing prayers into coverage and Williams was hauling them in as a good jump-ball receiver.
That is not sustainable though. While you can come up in certain moments you cannot be a consistent, true top receiver if you cannot get open consistently. That is why he is inconsistent.