The start of construction was delayed for a year because the club couldn't secure the necessary funding.
https://www.thetimes.co.uk/article/arsenal-stadium-delayed-until-2006-6cgtswmddm0. Arsenal had the luxury of building on a new site after failing to buy Wembley from the FA. Took well over 2 years to build as well. A lot of effort to build a dance hall for Jesse Lingard.
If Arsenal were knocking down Highbury and building a new stadium in it's place, if they couldn't secure the funding in time they'd be looking for a temporary home too.
It's a hugely complex project and 6 months or so delay is immaterial to the end result. The club already secured an alternative venue to play games at, should it overrun. It will be ready for next season regardless. All major construction projects overrun, it's just one of those things.
If laughing about it makes you feel better, all the better for you.