What is the reason why the conversion rate declined by 70% after AMP compliance of the website?

AMP is a framework for mobile websites proposed by Google, and it is possible to dramatically shorten page loading time by AMPizing the website. Nathan Contony who is CTO (Chief Technology Officer) at Rockstar Coders , a software development company, has responded to the up conversion rate (percentage that has resulted in the number of visitors per website) so far It has expanded to the level of 500%. However, when converting its website to AMP, the conversion rate has fallen by 70%.

Google AMP - A 70% drop in our conversion rate. - Rockstar Coders
https://www.rockstarcoders.com/google-amp/

Mr. Contoney was successful in raising the conversion rate to 500% by doing all correspondence to the website of Rockstar Coders. And since Google explained that "We might rank search results of sites that are compatible with AMP higher than noncompliant sites," he says he decided to follow AMP compliance next.

And as a result of continuing correspondence for several weeks, Rockstar Coders' AMP compliance was completed. Mr. Continy was convinced that the conversion rate would rise further, but I was waiting for the fact that after conforming to AMP the conversion rate fell by 70%.

Mr. Contony said, "Although it is difficult to identify what is the cause, as the cause of the decline in the conversion rate is various factors," three candidate causes are cited.

The first point is the URL. For AMP compatible pages, the URL becomes the Google domain. Normally, even if articles on news sites are delivered in the domain of Google, there is nothing to worry about, but when it comes to business, the story changes. Security problems may occur due to phishing scams etc in recent years. Because of this, Mr. Contoney says, "No one would like to access the dubious URL website," and speculates that it may be one reason that the conversion rate is lowered.

The second point is that "the page can not be displayed despite the AMP compliant page". Below is the web tool of Rockstar Coders displayed by Google Chrome developer tool, but a blank page is displayed even though there are no errors in particular.

According to Mr. Contoney, "Although this screen is displayed, it can be avoided due to coding problems", the frequency of displaying this screen is not high, it seems that it was not displayed in the internal test. It goes without saying that after the AMP compatible site was released in this state, the customers who displayed the pure white screen continued. And by impressing customers "Rockstar Coder's technical power is low", there is a possibility that the conversion rate will be reduced. Mr. Contoney says about this problem, "It is a phenomenon caused by proprietary JavaScript implemented in AMP," and states that it is a troublesome problem not to be noticed if careful testing is not done.

The third point is that the layout collapses. In fact, Mr. Contoney did take the time to do AMP correspondence, but it was not able to display exactly the same as the website before AMP correspondence. Below is an image comparing the layout before AMP (top) and the layout after AMP (bottom). Although it was able to fit the title line with 2 lines before correspondence, it is 3 lines because it can not reproduce this state on the screen after AMP correspondence, layout collapse has occurred. Similarly, because there are other pages whose layout has collapsed, change in design may also affect the conversion rate, Mr. Contony said.

Finally, Mr. Continy said, "Of course, not all of the reasons they lowered the conversion rate by 70%", but while taking the time to spend more time than planning to implement AMP compliance for the purpose of increasing the conversion rate, We need to make a website that is the same as before.