The new 'T7' is a MPV, more Sharan than van.So I think that is the irony. My tiny Tiny Model 3 has a huge battery. It must be a significant part of the overall weight. The same size battery would be a much smaller fraction of a van weight.
I think the real problem is the Van is very inefficient compared with the Tesla unless you measure it on energy per kg of cargo, in which case the van still rocks. The T6.1 will have a drag coefficient much higher than the 0.208 for the Tesla (T5s were 0.33) which significantly increases the power draw at speed, and all that weight uses energy to accelerate in stop start situations (even if a bit is recovered when you brake). That would require a much larger battery for the same range, which a T6.1 size vehicle could handle easily if designed into the floor plan in the same way as electric cars, but that would be ruinously expensive at today's prices, and ironically would add extra weight, which would need more batteries.
Looks like the new T7 will do 50mpg with the petrol engine so clearly there is more they can (and will have to do) to improve the efficiency of commercial vans ahead of the ban on new petrol and diesel engines in 2030 but we also need to hope for cheaper, lighter and more dense energy storage before then and I believe we will rise to the challenge.
We won't get a proper electric Transporter, we'll have to wait and see what Ford do to the Transit when they put a VW badge on it.